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.

My IT department will not turn on the feature in our servers that would allow me to receive corporate email on my iPhone. This has forced me to revert back to my BlackBerry Pearl. Can I transfer my iTunes music to my Pearl?

It depends on what you mean by “iTunes music.” If you mean music you bought from the iTunes store in protected format — which describes most of the store’s catalog — the Pearl can’t play it, unless you go through a laborious multistep process to convert it to unprotected files. If you mean unprotected music that is managed by the iTunes program on your PC, the Pearl can handle it as long as it is in open formats supported by the Pearl, including the MP3 or open AAC formats.

To get these files into your Pearl, simply use the music-transfer software that came with the Pearl to copy the songs from your computer’s hard disk to either the Pearl’s internal memory or to a flash memory card you may have in your Pearl.

I recently purchased a new iMac with the Leopard operating system, and have installed Windows Vista on it as well, using Leopard’s Boot Camp feature, so the Mac can boot into either OS. I would like both of those operating systems to share an external hard drive so I can back up my files. Is it possible to do that?

Yes, provided you follow one of two scenarios. The first would be to format the external drive as a Windows drive, but be careful to use the Windows format called “FAT32,” not the one called NTFS. Out of the box, Macs can see all Windows drives and can read from them all. But they can only save files to Windows drives that use the FAT32 system for organizing files. The downside of this is that the FAT32 system only allows files of up to 4 gigabytes each.

The other scenario would be to use a Mac-formatted external drive, which doesn’t have that limitation. Of course the Mac operating system can handle such drives perfectly, but Windows can’t even see them. However, in your Vista setup, you can install a third-party Windows program called MacDrive 7, which allows Windows to both read from, and write to, Mac-formatted drives. I have tested it successfully with Vista under Boot Camp on an iMac. The $50 program can be downloaded from mediafour.com.

The hard disk on my new Sony VAIO laptop is filling up fast. It is trying to get me to watch a lot of movie trailers. Is all that video stored in my machine somewhere and if so can I dump some of it out?

If your Sony laptop is like mine, not only are the unwanted movie trailers pre-loaded on your hard disk, but so are the entire movies, which Sony actually charges you to watch. In my case, these files took up over 4 gigabytes of precious disk space. This is a particularly outrageous example of what I call “craplets,” unwanted trial software that litters new Windows desktops. You can delete these files and reclaim all that disk space without any harm to your computer.

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