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.

I have a laptop that I use primarily to play music. Is there any way to disable its connection to a wireless network?

Sure, but exactly how you do that depends on the laptop’s hardware and operating system. Some Windows laptops have a hardware switch, or a keyboard function — often identified by some sort of transmitter icon — that turns the Wi-Fi wireless radio inside off. If yours does, just use these hardware controls to kill Wi-Fi.

Others require disabling Wi-Fi via software. In Windows XP, go to the Network Connections control panel, find the Wi-Fi connection, right-click on that icon, and select “Disable.” In Windows Vista, go to the Network and Sharing Center control panel, locate the wireless network, and click the “Disconnect” command in the information area under its name. On a Mac laptop, you can just click on the fan-like Wi-Fi symbol in the menu bar and select “Turn Airport Off” (”Airport” is Apple’s term for its Wi-Fi radio).

If your Windows laptop uses an application other than control panels to manage your Wi-Fi connections, you may have to disable them from within that program.

Thanks for your column on netbooks. Which of the netbooks came pre-installed with Microsoft Office? For those that didn’t, how can you install Microsoft Office onto the device?

I tested only four models, all running Windows XP. None came with a full, activated version of Office installed. Two — the Acer Aspire One and the MSI Wind U100 — came with trial versions of Office pre-installed. Another, the Asus Eee 1000H, came with an alternative office suite, StarOffice. Two, the Asus and the MSI, came with a stripped-down office suite, Microsoft Works.

The simplest way to install Office, or any other software that comes on disc, onto a netbook is to plug in an external DVD drive using a USB port.

I have two questions about the iPhone. My first question is whether or not it’s possible to tether the phone to a computer for use as a modem. My second question is whether it’s possible to rent or buy movies on the phone itself or if that needs to be done from a laptop or desktop?

It isn’t currently possible to use the iPhone as a tethered modem, but AT&T recently said that functionality might be coming. It also isn’t possible to buy or rent movies directly on the phone, only music. You have to transfer movies from a computer.

• 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.