I get confused by all the different models of the BlackBerry — Bold, Storm, Curve, Pearl and so on. Can you briefly explain the differences?

There are too many models to list here, because RIM, the maker of BlackBerry, makes varying versions for competing wireless carriers, and these may have different features, even if they look the same. However, here’s a quick breakdown of the main flavors.

The Bold is the top-of-the-line BlackBerry, relatively large and costly, with a wide keyboard and a big, vivid screen. The Curve is its little brother — still sporting a good, full, keyboard, but lower-priced, smaller and lighter. The newest Curve, called the 8900, has a beautiful screen and is even sleeker than its predecessor.

The Pearl is a slimmer, low-priced, more fashion-oriented model with a truncated keyboard that has two letters on each key and relies on software to guess which one you meant to hit. The Pearl Flip is much like the Pearl, except, as its name implies, it’s a flip phone.

The Storm is the BlackBerry line’s most direct competitor to the Apple iPhone. It’s the only BlackBerry without a physical keyboard, instead relying on a large, beautiful touch screen for typing and navigation. Unlike on the iPhone, however, the Storm provides physical feedback each time you press down on the screen.

I’d be interested in the new, tiny iPod Shuffle, except that I dislike Apple’s earbuds. And, because they have now moved the playback controls to the earbud cord, I can’t use my favorite third-party set. What are my options?

Well, one option is to buy the old model of the Shuffle, which Apple is keeping on the market. It’s larger, but still very small, and has the controls on the player itself, rather than on the earbud cord, so you can use plain old earbuds or headphones from other companies. Plus, at $49, it’s $30 less, though it has only 25% of the capacity of the new one and lacks the new model’s voice features.

Another, costlier, option is to buy better earbuds that have the new controller built in. Apple sells a pair of $79 in-ear buds with a control module on the cord. They were designed for the iPod Touch, but the company says they work perfectly with the new Shuffle. Several other headphone companies, such as Klipsch, have announced plans to offer either headphones or adapters with Shuffle-compatible controls in coming months.

Is it safe to upgrade my Vista PC to the beta version of Windows 7?

Since it is a beta version, there is always some danger of problems. But I have upgraded a couple of Vista computers with no special tricks or help, and with no significant problems. Still, there are a couple of caveats. First, Microsoft will be replacing the beta with a more polished “release candidate” that could involve a re-installation process, so you may want to hold off. Second, Microsoft isn’t guaranteeing that every hardware feature on every computer or peripheral will work properly under the pre-release versions.

• 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 in the market for a new Windows computer, but I prefer the Windows XP operating system, not Vista. I understand Microsoft has now barred the major PC vendors from selling XP systems. Is there a way I can get around this?

If you want a new, brand-name PC that comes pre-loaded with the seven-year-old Windows XP operating system, you can still get one through an odd and circuitous process. Most major PC makers will sell you selected Vista models with an option, which sometimes costs extra, officially called a “downgrade,” but sometimes marketed as an “upgrade” or “bonus.” You may have to hunt through the selections offered by the computer makers to find one that has this XP option.

When you order a PC in this fashion, you are technically buying a Vista machine, and Microsoft counts it as a Vista sale. But the computer company actually loads XP on the new hardware, in place of Vista, before it leaves the factory. In many cases, you also get discs containing Vista, in the event you wish to switch to the newer Vista operating system later.

I was wondering if you could give me some suggestions of a small, light portable radio-type gadget with earbuds that would be good for me while I do athletic activities like riding my bike. I want something that will give me different pre-programmed selections of music, not something that I have to load with music (I don’t remember names of songs). I love my Sirius satellite radio in my car.

My first reaction is to suggest you simply get the portable, small, personal Sirius radio that is meant for carrying on your person. It’s called the Stiletto 2 and costs around $300. Like the one in your car, it does require a subscription, but it is much smaller. I haven’t tested it, but you can get more information at sirius.com.

However, this unit isn’t in the smallest class of portable music players, so another alternative might be to get a very small portable player, which, while it allows you to download music, also has a built-in FM radio. Among these is the smallest Microsoft Zune, called the Zune 4 GB, at about $100, and the Sansa Clip, starting at about $35. Neither requires a subscription fee. Information is at zune.com and sansa.com.

The popular Rhapsody subscription music service is also available on portable players, and offers pre-programmed channels of music. Some of these players also include FM radios. Information on these is at learn.rhapsody.com/devices.

Last week, you said you didn’t know of a dedicated gadget that simply allows people to both send and receive emails. What about the MailBug?

Thanks for reminding me. The MailBug, which I haven’t tested, is a small, text-only terminal for sending and receiving email over a dial-up connection. It costs about $125 and requires a companion email service that is about $100 a year. It’s made by a company called Landel and can be ordered at mailbug.com.

While the device itself can’t send or receive photos or other nontext attachments, account holders with access to a computer can view such attachments via a Web-based version of their email accounts.

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