A: The built-in backup program in your iMacs, called Time Machine, doesn’t require Apple’s Time Capsule product to work. It will work with almost any brand of directly connected external hard disk.

For instance, I back up my home iMac to a Western Digital drive that’s connected to it via a cable.

As for hard-drive life, it’s my experience that many seem to die sooner or later, especially if they are used heavily. I don’t know if the ones inside the Time Capsule are especially fragile. But, in just the past six months, I’ve had an external hard disk from G-Tech die on me; seen an internal hard disk on my home Dell die for a second time; and discovered that the hard disk on my colleague’s MacBook died.

One way to protect against the failure of a local backup drive is to consider, in addition to using an external disk, backing up your data to an online backup service like Mozy, Carbonite or SugarSync.

My Dell has Microsoft Vista but I can upgrade free to the new Windows 7. However, I was told my antivirus software won’t be compatible and my email will change—the program will no longer be “Windows Mail.” What do you recommend?

A: I regard Windows 7 as much better than Vista, but you are correct that many antivirus programs will require upgrading and Windows Mail will go away during the upgrade. You’ll have to install a new email program, such as the very similar “Windows Live Mail,” which can import your messages. So, the question really is one of trade-offs. If you’re satisfied with Vista, and would rather not perform these program replacements, you should stand pat. If you don’t like Vista, and are anxious to replace it, then the hassles you describe could be worth it.

Will Office 2003 work with the new Windows 7 operating system?

A: Microsoft, which makes both products, says the answer is yes, though I haven’t tested it.

Is it possible that the Verizon Motorola Droid, which doesn’t work in Europe, could be turned into a “world phone” that could work on European cellphone networks via an app somebody might develop?

A: An app wouldn’t be able to do that for the current Verizon Droid. It’s a hardware issue.

Verizon’s Droid, like most Verizon phones, is built to run on a type of network called CDMA that isn’t used in Europe or most other countries outside the U.S., which use a network standard called GSM.

To run on these networks, the Droid, or any other current CDMA phone, would need an entirely different radio, or two radios, one for each type of network.

Verizon offers a handful of so-called “world phones,” which have both kinds of radios inside, but the Droid isn’t one of them. Motorola may well make a new model with two radios, or even a model with one radio that would work overseas, and I wouldn’t be surprised if it did so.

What could be done with an app is to allow the Droid to make so-called VOIP phone calls via the Internet.

In fact, while I haven’t checked, there may already be such an app for Android—the Droid’s operating system—that would do so. But, in many cases, making such Internet phone calls requires the user to be in range of a Wi-Fi network. Some carriers don’t allow such calls to be made over their cellular networks.

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

Here are a few questions about computers I’ve received recently from people like you, and my answers. I have edited and restated the questions a bit, for readability.

I am going to start college in the fall and I need a laptop. Uncle Jim, who is a Mac addict, is making an argument for a MacBook with Parallels 3.0 and Windows XP installed. He said that way I would have the best of both worlds. My mom is looking at the price. She said we could get a PC for less money but I want to make sure we’re making the right decision. If money is not an issue, what is your recommendation?

Both your mom and your uncle are correct. You can indeed get a decent laptop from Dell or Hewlett-Packard for less than the $1,099 that Apple’s least expensive Mac laptop, the MacBook, costs. But, in my view, the Mac has a better, faster operating system, better built-in software, and is far less likely to expose you to viruses and other malicious software. Plus, the MacBook itself is a sturdy piece of hardware. And there’s a very good Mac version of Microsoft Office that is fully compatible with files created on the Windows version.

Your uncle is also correct that Macs can run Windows, and Windows software, quite well. However, the solution he suggests, using the Parallels software, which enables Windows use on a Mac, will add significantly to the price. Parallels costs around $60, and you also must buy a full, boxed edition of Windows XP or Vista. While prices for Windows vary, this full version (not an upgrade version) of XP can cost nearly $200, and Vista typically costs more.

So, if money really isn’t an issue, I recommend the MacBook. But, since that is rarely the case in real life, you might want to weigh the cheaper alternatives more carefully. Or, if you do buy the MacBook, I’d hold off on the Windows installation until and unless you find you need Windows programs that have no counterpart on the Mac. The average undergraduate likely won’t.

I am dissatisfied with my Internet service provider and I would like to switch to another one. If I switch, can I keep the same email address? Do I have to keep paying the old ISP if I switch and keep the email address?

It depends on your ISP. If it is America Online, you will be able to drop AOL as your ISP and continue to use your aol.com address, regardless of which provider you use to access the Internet. But, in most cases, if you are using the email address provided by your ISP, you will have to relinquish it. However, I would suggest you consider obtaining an email account that isn’t tied to an ISP, so that, if you have to change ISPs again, it won’t disrupt your email. Among such email-only services are Yahoo Mail, Microsoft’s Windows Live Hotmail, and Google’s Gmail.

Your column last week concerned a navigation device called Dash Express that transmits the speed and location of your car to the company for traffic information purposes. But couldn’t this capability also be misused by the company to track a driver’s whereabouts, or even help issue speeding tickets?

Theoretically, yes. But the company, Dash Navigation, says it retains no personally identifiable information on its servers, and merely collects traffic data from participating cars anonymously. A company spokeswoman says: “If the FBI came in and asked us to find someone, we would have no way of locating an individual car.”

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.

I am considering the purchase of the MacBook Air (AAPL). If this computer freezes up, as my current Dell Inspiron does on occasion, how would I correct for that? I usually remove and then replace the battery on the Dell (DELL). But what would I do if this happens with the Air, since it has no removable battery?

You can force a frozen MacBook Air — or any current Mac laptop — to shut down and restart without removing its battery. You just hold down the power button for a few seconds until the machine shuts off, then wait a few seconds, then turn it on again.

I am a Verizon (VZ) customer and have a Palm (PALM) Treo 700W for personal use. I would like to replace the Treo but, in light of Verizon’s announced “open network” policy, I am wondering if this is the right time.

It’s far too early to know what new phones will be available under the new Verizon program, since that depends on which phone makers decide to make devices to run on the “open” network, and what kinds of devices they might produce. There is the potential for phones that are more creative or interesting than what is available today, but it’s only a potential. Verizon has just laid out the first details of the plan, and no product announcements are likely for quite a while. If your Treo needs replacing soon, and you want to remain a Verizon customer, you will have to choose from the company’s current smart-phone offerings.

Are there any cellphones that allow for two separate phone numbers? Right now I carry two devices, both with the same carrier.

At least in the U.S., each cellphone, or each SIM card that goes in a phone, is normally tied to a single number. To use two numbers on a single phone, you could purchase an unlocked phone running on a GSM network and then purchase two SIM cards, each with a separate number, and swap them in and out. But that would be an inconvenient process, since inserting and removing SIM cards typically requires opening the phone and even removing the battery.

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.

I have a USB cell phone data card that I use with my laptop. This card offers me world-wide connectivity wherever there is GSM cellphone service available. Is there an adapter that will allow me to use this card with the iPod Touch?

I know of no such adapter, nor of the software that would be needed to make one work. However, although the iPod Touch has no cellphone capability, it does include Wi-Fi, which can give you high-speed Internet access world-wide whenever you are in range of a Wi-Fi wireless network.

What U.S. cellphone service provider should I consider when purchasing a new contract and phone that can be easily used in most western European countries and also get good coverage in the U.S.?

In the United States, the only two major carriers that use the technology compatible with European networks are AT&T and T-Mobile. As to which has better coverage in the U.S., my own anecdotal experience is that this varies greatly depending on where you are, and that neither has coverage that’s as good as Verizon’s in as many major cities. However, Verizon (like Sprint) uses a technology that isn’t compatible with European networks, though it has one or two phone models that include both technologies.

I have just switched to the Mac from Windows. Is there a tutorial somewhere on how to use the Mac user interface and operating system?

There are a couple of books on switching to the Mac, which you can find at online bookstores. Also, Apple maintains two free, illustrated online tutorials called “Mac 101″ and “Switch 101,” the latter being specifically for former Windows users. They are available at apple.com/support/mac101 and apple.com/support/switch101.

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