All of the major digital maps contain erroneous information about our street in Virginia, and don’t even show several new streets near our home that were built over three years ago. I infer that there is one source of cartography used by these Web services, and also by my Garmin navigation system. But I can’t find out what it is. How can an individual get something like this corrected?

There are actually two main companies that make the underlying maps that most of the navigation-device makers and digital-map sites use. One is called Tele Atlas (TLATF.PK), and one is called Navteq (NVT). Garmin (GRMN) uses Navteq. Each mapping company has a Web page where users can report errors or changes.

For Navteq’s error-reporting Web page, go to navteq.com and click on “Map Reporter.” For Tele Atlas’ similar page, go to teleatlas.com and click on “Report Map Changes.”

In reading your review of the new Gogo in-flight wireless Internet system, I wondered about two things: Does it support “virtual private networks,” and when will it be installed on Amtrak trains?

While I didn’t test this, Gogo’s maker, Aircell, says that VPNs, which are used by many big companies, do indeed work over the service.

As for Amtrak, the Gogo system wouldn’t work for trains, because its antennas point up, into the sky, and don’t cover ground locations like railroad tracks. However, if you are on an Amtrak train in an area where cellphone towers are near the tracks, and your laptop computer or cellphone can pick up cellular data signals, you can already surf the Web and do email and other online tasks on the train.

In fact, I happen to be writing this column on an Amtrak Acela train between Washington and New York, and, using a Verizon (VZ) laptop card, my laptop is able to access the Internet with only occasional lapses.

Because of problems I had with my computer, I lost my Internet Explorer favorites. How can I save them so I can easily restore them if they get wiped out again?

There are several methods. You should, of course, be backing up all your key data, including your browser favorites or bookmarks, regularly, either to a local external disk, or to an online backup service. That would create a fairly fresh backup of your favorites. You could also use one of several Web sites that specialize in hosting, and sharing, bookmarks or favorites. They allow you to add bookmarks to your online list as you surf, and also to upload and download the favorites and bookmarks you keep locally on your computer. The best known of these sites is probably del.icio.us, which is at http://del.icio.us.

The simplest method, however, is probably to just export your favorites to a file and save it in your Documents folder, on your desktop, or on a USB thumb drive. You can then use this file to restore your favorites in case of disaster. To do this in the latest version of Microsoft (MSFT) IE, click on the “Add to Favorites” button, select “Import and Export,” click “Next,” then click “Export Favorites” and walk through the steps that follow. Detailed instructions for all versions of IE are at: support.microsoft.com/kb/211089.

• 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.

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.

We are connected to Comcast (CMCSA) cable and use no antennas. Will we need one of the government-subsidized converter boxes next February?

Not if you are using a cable set-top box, like the vast majority of cable customers. If you are one of the minority of cable households whose TVs use an internal cable tuner, you may need a converter box. To be sure, contact your cable company or TV manufacturer.

In your laptop buying guide last week, you recommended buying a machine equipped for the “n” type Wi-Fi of wireless router. I was under the impression that this has not yet been standardized. Is that wrong?

The engineering committee that has been debating the standard for years has not yet completed its work, but the market has simply moved ahead on its own. This new, faster version of Wi-Fi is being built into routers, computers and other devices by nearly every major manufacturer. In my limited tests, I have found no compatibility problems, and it is backwards compatible with the older “g” and “b” standards.

Is the Mac immune to viruses? If not, do you have a recommendation of the type of antivirus software one should procure and load onto a Mac?

No personal computer or personal computer operating system of which I am aware is “immune” to viruses, spyware or other malicious software. That includes Apple’s (AAPL) Macintosh and its operating system, Mac OS X Leopard. Hackers have demonstrated the ability to invade the Mac. However, there are only a handful of viruses or other malicious programs for the Macintosh that have successfully spread beyond the lab. And these have harmed only a small number of actual users.

Of the well over 100,000 known viruses, spyware programs and other malicious software applications that are about in public, all but this handful are written to run on Microsoft (MSFT) Windows, and cannot operate on the Macintosh OS. For that reason, I don’t believe Macintosh owners need security software, unless they install and run Windows on their computers. If they do run Windows, Mac owners are well advised to purchase and install Windows security software to protect the Windows portion of the machine.

Having said that, I do not mean that Mac owners should be blind to security threats that don’t involve viruses or spyware. Just like Windows users, Mac users can succumb to what is called “social engineering” — scams and schemes that operate via email and Web sites that are often authored by crooks but made to look official. So, like Windows users, they must be on their guard.

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

On TV, they announced a $40 government-issued coupon that is available to offset some of the cost of the new digital converter boxes we will need for our older television sets. How do I go about getting some?

You can apply for a coupon at a federal government Web site designed expressly for that purpose: www.dtv2009.gov. Or, you can call 1-888-DTV-2009 (1-888-388-2009). Each household can receive up to two of the $40 coupons, which look like plastic gift cards, but they can’t be combined to purchase a single converter box. Each coupon must be applied to the purchase of a separate box, which the government estimates will cost between $50 and $70 at popular electronics stores. Coupons also must be used within 90 days of the date on which they are mailed to the consumer.

Note that these converter boxes won’t be needed for about a year, and aren’t necessary for TV sets containing digital tuners, also called an “ATSC” tuner. Such tuners have been included in many TV sets sold in the U.S. since 2004, even if they aren’t high definition televisions. Converter boxes also aren’t needed for older analog TV sets that receive their programs via cable or satellite services or other pay services. They are needed only for older analog TV sets that depend on free, over-the-air programming, the kind usually received via an indoor or outdoor antenna.

Is it possible to transfer data from a computer with Windows 95 to a computer which uses Windows XP?

Yes, but the trick would be to figure out a medium for the transfer. Many, if not most, Windows 95 PCs don’t have USB ports, which rules out using a USB thumb drive or external USB hard disk as the transfer mechanism. If your old PC can burn CDs, that might be a good way to transfer your data.

Another option is buying a program like LapLink’s PCMover, which explicitly supports Windows 95 and can automate the process using either a network, removable media, or parallel cables. See laplink.com for details.

I’m thinking of getting an iPod Touch to replace both my iPod shuffle and Palm Pilot Vx. Does the Touch have as good address book and to-do functions as the Palm has? Does the Touch sync to the Mac’s Address Book, Mail, and Calendar software? If so, would it also sync to a Windows box?

The iPod Touch, and its close cousin, the iPhone, do have what I consider to be a very good address book, or Contacts program, though it may not have all the same features you use on your Palm. And that address book can be easily synchronized with a computer.

On a Mac, the iPhone and Touch Contacts can be synced with the built-in Address Book, or with Entourage, Microsoft’s Outlook equivalent. On a Windows PC, it can be synced with Microsoft’s Outlook; with Outlook Express (Windows Address Book) in Windows XP; or with Windows Contacts in Windows Vista.

The calendar on the Touch and iPhone can be synchronized with the Mac’s built-in calendar, with the calendar in Entourage, and with the calendar in Outlook on a Windows PC.

However, neither the Touch nor the iPhone includes a true to-do or task function, and neither synchronizes email with a computer. They do have a good email program, but it is intended to work on its own, fetching and sending email directly, rather than copying email from 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.