USB flash drives are great, aren't they? You pop your files onto one, drop it into your pocket, and then get to the files from any computer with a USB port. Unless, of course, you happen to lose the USB flash drive, in which case, well, your files are lost too.

That might not be too much of a concern if the files in question are copies of holiday snaps or a few tunes. There is irritation, sure, but not a lot else. But if the files are important work documents, you might be more worried.

Password protection for your USB flash drive and its contents is just one of the features offered by U3, a standard that turns the humble USB flash drive into something entirely new.

Another key feature of U3-capable drives is that you can run applications from them. This has two benefits. First, you can carry software with you and be sure that wherever there is a USB port on a PC you can run it. Second, the software runs entirely from the USB flash drive, not from the PC: no documents you create, no cookies you download, no passwords you enter, no e-mails you send, ever get left on the PC.

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Sounds wonderful, but you do need to bear an important caveat in mind, namely that software needs to be specially tweaked to work with U3. So far the range includes a lot of very good freeware, such as OpenOffice.org for word processing, spreadsheeting, drawing, presentations making and databases, Trillian for instant messaging, Skype, Firefox, Thunderbird and so on.

And there are paid-for applications which can synchronise files with your PC, help you do e-mail, manage passwords for Web sites, run photo slideshows, play your tunes and more. But you won't see any really big name applications in the lists at www.u3.com, even though the developer software required to tweak applications is free of charge.

In our tests the Kingston drive performed faultlessly. We installed a heap of freeware and then Web browsed, Skyped, Trillianed and created documents without any bother at all, and without leaving a trace on the computers we had been using. And, because there is nothing to stop you using the drives for simply carrying files around, we did that too, taking music, photos, documents and more between computers in the usual USB flash drive way.

U3 isn't in itself going to protect you from every possible nasty. You can copy files to a computer hard drive, in which case, of course, they need to be removed again if you don't want to leave them behind. Keyloggers can probably still log keystrokes, and if you copy a virus-infected file to a drive from a PC you are using and then fail to check before you copy it onto your main PC, you could be in trouble. But yes, there's some anti-virus software you can buy for U3 flash drives.

Ultimately, the whole thing is a step in the right direction, and being able to password protect the drive itself means that if you do happen to lose it, your vital documents - or photos, or music - will be safe from prying eyes.

U3 has yet to really catch on, but when it does, old fashioned, unprotected USB flash drives look set to disappear from view.