Last week, when you wrote about the ChaCha cellphone search service, you didn’t say how they make money. Are they collecting phone numbers from customers so they can send spam text messages, or sell the numbers to others who will do so?

ChaCha allows you to ask any Web-searchable question, by speaking it or texting it over a mobile phone, and then it sends you the answer via text message. The company charges consumers nothing, but says it is hoping to make money by striking deals with cellphone carriers to incorporate the ChaCha service into their current 411 phone-number look-up services. Also, it hopes to eventually include ads in the text message answers it provides.

In addition to the message that includes the answer, ChaCha sends you a message saying it is working on your request and restating your question, so you can see if it understood you correctly. It also sends an introductory text message to first-time users and occasional tips on how to use the service. Scott Jones, ChaCha’s chief executive, asserts that “we do not spam” and “we never make phone numbers and/or email addresses available to others.” He said the company is updating its privacy policy to make that clearer.

We have DSL service. I use several Web-based applications, one of which is online backup, and my husband is concerned that they degrade his use of the Web, which includes creating Web sites. I contend that that is like saying turning on one light bulb is using too much electricity, that two people on one DSL line aren’t using up too much bandwidth. Who is right?

Every situation differs, depending on exactly which programs you are each using, how you have them set, whether you are using them simultaneously, and how fast your DSL connection is. However, in general, your husband is correct that it is possible for heavy Internet usage on one computer in a home to slow down Internet speeds on another.

This is especially true with something like online backup, because it relies on your DSL account’s upload speed, which is typically far slower than the download speed. If your online backup program is trying to push a bunch of files over a slow upload connection, while he is in another room trying to upload new versions of a Web site over the same narrow upload pipe, it could affect the speeds he gets. You might try coordinating or staggering those online activities that involve heavy uploading. Normal Web surfing or emailing shouldn’t require any such coordination.

I am thinking about purchasing a Dell (DELL) XPS One all-in-one desktop, but I have one question. Does the Dell’s built-in TV tuner require any extra attachments to watch TV right out of the box?

You can watch over-the-air stations and analog basic cable stations right out of the box, without added equipment. However, you may want to connect a small desktop antenna to improve reception, which is what I did when I tested this machine. To use the XPS One with digital or premium cable or satellite stations, you would have to connect it to a cable or satellite receiver, just as most people do with their TV sets. This requires the use of an adapter that comes with the machine.

• You can find Mossberg’s Mailbox, and my other columns, online for free at the new All Things Digital web site, http://walt.allthingsd.com.

Has anyone come up with a method that allows people to take pictures with a regular digital camera and then download them wirelessly to a computer, and/or perhaps to the Internet?

There have been a few digital cameras with built-in Wi-Fi wireless capability, but the best and simplest method I know is a $100 product called Eye-Fi. This tiny gadget looks and works like a regular, garden-variety SD memory card, but it packs a Wi-Fi transmitter inside. It fits into a standard SD memory-card slot and is compatible with a wide range of camera models from Canon (CAJ), Kodak (EK), Nikon (NINOF.PK) and others.

Coupled with clever software, and a clever Web site, the Eye-Fi card automatically zips your pictures wirelessly to your PC or Mac, and/or to your choice of over 20 online photo-sharing services.

For more information, see www.eye.fi. For a list of compatible cameras, see support.eye.fi/compatibility/. For a full review of the product, see: solution.allthingsd.com/20071121/.

You mentioned last week that SugarSync might be a good solution for backups, so if one computer dies your files still exist on another system. But what if the doomed computer doesn’t actually die but its files are corrupted by malicious software? Do those newly corrupted files overwrite the good copies on your SugarSync network?

They could do so, depending on which folders you had chosen to replicate on your other computers. Automatic-synchronization services like SugarSync have a tough time telling whether changes to a file are deliberate, accidental or the result of some sort of corruption. Though the last is rare, it could look to SugarSync like you had changed the file on purpose.

One way to guard against that is for a service to offer “versioning” — the practice of maintaining multiple past copies of a file. That way, if a change isn’t intentional, you can go back to the prior, pristine version. Sharpcast, the company that makes SugarSync, says it is planning to add versioning to the service, but offers no specific date. In the meantime, one way to back up a file without fear of its being overwritten by a corrupted version is to upload it to SugarSync’s special “Web Archive” folder, whose contents are never automatically updated.

Have you ever reviewed and suggested a media player for connecting to a home theater to play all songs, videos and photos that exist on your home computers?

Yes, I have reviewed several over the years. The one I find simplest and best designed is Apple TV, which, despite its name, can work fine in a household with no other Apple (AAPL) hardware. It costs $229 and is a small, thin, unobtrusive box that fetches music, photos and videos from your home network using either a wired or a wireless connection. It can connect to your TV set or home theater via a variety of analog and digital ports, including component-video, HDMI, and optical and analog audio. It supports high-definition video and works with any computer, Windows or Mac, that has Apple’s free iTunes software installed and running.

Apple TV handles many standard photo, music and video formats, but it is limited to music and video files that iTunes can handle. That excludes copy-protected files in Microsoft’s formats, and certain open Microsoft formats, but includes common files like MP3s. Apple TV also allows you to access YouTube and to purchase music and TV shows from Apple, and rent movies from Apple, without the use of a computer.

• You can find Mossberg’s Mailbox, and my other columns, online for free at the new All Things Digital Web site, http://walt.allthingsd.com.

I have a new H-P (HPQ) laptop and there are several preinstalled media-playing interfaces that have been foisted on me. Do I really need all of these interfaces? Can’t I just get all of this media to run through Windows Media Player or iTunes?

Since you weren’t specific, I don’t know what media software came with your new laptop. I’m sure some of it may have been redundant “craplets” — the unwanted software PC makers load onto their machines in order to collect a fee from the programs’ publishers. And you are correct that many of the most common audio and video file types can be handled by Windows (MSFT) Media Player and iTunes.

However, the Internet is full of media file types that are best played, or can only be played, in specialized software — either separate applications on your computer or online players that are enabled via your Web browser. So, over time, most users will collect additional players, or plug-ins for their Web browsers, that will supplement their main media-playing program. One way to see if the media software on your new computer is necessary is to test what types of files it handles. If you can open and play these same files in Windows Media Player or iTunes, and you prefer to do so, then you probably don’t need the added software.

If I am running Windows Vista on my iMac desktop using Parallels, will Apple’s Time Machine backup program automatically preserve the Windows hard disk, too?

Yes. Parallels, and its competitor, VMWare Fusion, create virtual Windows hard disks inside a Macintosh. When you are running Parallels or Fusion, Windows sees these virtual hard drives as if they are distinct physical disks. However, they are in fact just very large files on your Mac’s hard disk. So Apple’s (AAPL) Time Machine backup program treats them like any other file and backs them up. Time Machine can also restore these virtual Windows hard disks, in their entirety, just as it can restore other kinds of files.

There are some caveats, however. Time Machine treats each virtual Windows hard disk as a big, unified blob of data, so it cannot peer inside them to recover individual Windows files you may have accidentally deleted while running Windows programs. Also, if your virtual Windows hard disk is large, and it changes often, then using Time Machine to back it up may suck up a lot of space on your backup drive, as numerous archived versions of the file accumulate.

I currently have a DVD player and a large stack of DVDs that I play through my analog TV set. After the 2009 digital TV conversion, will I still be able to use my existing DVD player and play my existing DVDs, even if I buy one of the government-subsidized converter boxes?

The FCC says DVD players and other add-on gear “will continue to work, even if they are only analog-capable.” But it adds that “manufacturers are producing a number of different connectors to hook equipment together and improve picture and sound quality. Check with your equipment retailer to determine the types of connectors that will work with your equipment.”

In other words, while there’s no inherent conflict, it all depends on your particular DVD player, your particular TV set, and how you have them connected. The best thing to do is consult closely with the dealer or manufacturer selling the converter box so that you understand how it can coexist with your current DVD player setup, or how you might have to alter your current setup.

You can find Mossberg’s Mailbox, and my other columns, online free of charge at the new All Things Digital Web site, http://walt.allthingsd.com.

If I have an analog TV and get a government-subsidized converter box, will I still be able to use my VCR after the 2009 switchover to digital over-the-air broadcasts?

According to government and industry statements, a VCR will still work, but it will have to be connected to the output jack on the converter box to receive the programming it records, because its internal TV tuner will no longer work. Also, the quality of the taped program will be limited to the quality available in the older VCR, and won’t necessarily match the crisper quality of the new digital broadcasts when viewed live.

Recently, you recommended a program that tells people what programs start up when they boot up a PC. I have installed it. But how do I know which programs should be retained? There are a lot there, but I have no way to know which I can eliminate and which I should retain.

This is one of the maddening issues nontechnical folks face with PCs. Even when you know what invisible background tasks might be slowing down your computer, you lack the knowledge to decide which to kill or spare, because their names don’t necessarily tell you their functions.

One way to tell is to look them up on the Web. A Web site I have found useful for such research is called AnswersThatWork, at answersthatwork.com. Click on the icon labeled “task list,” and you will find a directory in which you can look up such programs. The site tells you what they do and recommends whether to delete or keep them.

Can you suggest a hardware box that can be attached to my TV that will keep all stations and commercials at the same level of volume? I’m going nuts having to keep my finger on the volume control of my remote.

A quick Web search turned up a couple of boxes that claim to do just that. These boxes connect between the TV set and a cable or satellite receiver.

One, a $30 device called the “TV Volume Regulator,” is sold by a Web site called Smarthome and is at: www.smarthome.com/7848T.html. The second, a $70 box called the “Automatic TV Sound Regulator,” is for sale at a Web site called firstStreet. Its Web address is: www.firststreetonline.com/product.jsp?id=55851.

There may be other, similar products out there. But I can’t recommend any of them, including the two listed here, because I haven’t tested any.

You can find Mossberg’s Mailbox, and my other columns, online free of charge at the new All Things Digital Web site, http://walt.allthingsd.com.