Microsoft's Windows Live OneCare service promises to keep your PC safe from malware and running as well as it did the day you first turned it on. But a bug in the latest version of the service has sabotaged opinions of OneCare, and for good reason: It was hiding or even deleting certain Outlook- and Outlook Express-based email data files. After two weeks of complaints, Microsoft quietly fixed the problem with a patch issued over the past weekend.

According to Microsoft, OneCare was erroneously quarantining (or, if manually configured this way, deleting) some Outlook 2002, 2003, and 2007 and Outlook Express 6.0 (the version in Windows XP) data files that contained infected emails. This caused users of those email applications to encounter errors as well as lost email messages. Curiously, Microsoft originally described this issue as the intended behavior, noting in an online support forum that quarantining such files would "protect your computer." You can imagine how this was greeted by frustrated users.

OneCare is configured by default to automatically download and install any patches when the PC is connected to the Internet, so most people running this service should have been updated by now. That will be of little comfort, however, to the people who have been suffering through this issue for over two weeks, many of whom lost email data for good.

Users with quarantined email data files can manually recover them from within OneCare. To do so, close your email application and click "Change OneCare Settings" from within OneCare. Then, navigate to "Viruses & Spyware" and click the Quarantine button. Then, select your Outlook PST or Outlook Express DBX file and click "Restore."

Microsoft's Windows Live OneCare service was introduced last year with great fanfare, and the company shipped a Vista-compatible version in late January. The release of the low-cost security suite caused security vendors like Symantec and McAfee to rethink their own products and release more competitive offerings. However, OneCare has been beset by problems in recent days and has fared poorly in malware detection and removal comparison tests. This latest issue has done little to bolster confidence in the product. Microsoft recently announced that it will issue a public beta of OneCare Live 2.0 in April.