Dave Methvin at PC Pitstop has an interesting -- and disturbing -- article in his company's monthly newsletter for April: Vista's slice-and-dice approach to carving its features into multiple versions has produced one presumably unintended side effect, he says: the less expensive Home Basic and Home Premium versions make backups of older versions of your files as you create new ones -- but you can neither access them, nor delete them.Methvin is CTO of the site, which offers online and downloadable testing, diagnostics and tune-up utilities for PCs. Methvin and Rob Cheng, who's CEO of PC Pitstop, tackle Windows Vista's System Restore function in their newsletter. Cheng notes that in Vista settting restore points is producing elephantine files as big a 8GB. Methvin is on about something related.

In his article is titled "Vista Backups You Can't Have" he writes about the Previous Versions feature in Vista. System Restore has been available in previous versions of Windows, but it worked differently. Previous Versions is new.

Vista's System Restore and Previous Versions features are both driven by the Shadow Copy technology in Vista. In fact, System Restore is enabled by default, and Vista sets aside 15 percent of your hard disk for Shadow Copy to use for copies of the system files that System Restore uses, and for the backups of your data that Previous Versions creates when, for example, you replace an older version of a file with a newer one. If you want to restore one of those older versions you just right-click on the file (it works for folders, too) and choose "Restore Previous Version" to open the properties box to a "Previous Versions" tab.

All six editions of Vista (Starter, Home Basic, Home Premium, Business, Enterprise, and Ultimate) include System Restore, but Microsoft left Previous Version out of the Home editions -- to encourage us to upgrade, says Methvin. But, he says, this feature partitioning has resulted in a situation where users lose control of their own data.

In Vista Home Basic and Vista Home Premium, without Previous versions you can't get to backups of your documents -- there's no "Previous Versions" in the properties box. But Shadow Copy makes the backups anyway, Methvin says. They're there, on your hard drive, but you can't access them. And you can't delete them.

Methvin says he discovered this when he used Microsoft's Windows Anytime Upgrade feature to upgrade a PC from Home to Ultimate: "When we did that, the Previous Versions tab appeared and revealed changes to data files that were made before the upgrade occurred."

There's no really good fix, for it, either, according to Methvin and Cheng: There's no way to selectively add or remove a file or folder from the backup, and disabling Previous Versions also requires that you disable System Restore and delete all restore points.

Cheng outlines a workaround that lets you permanently delete things one file at a time. But this sounds a little like a security problem waiting to happen, doesn't it?