Windows 7 chkdsk bug linked to antivirus software

Hard disk

Avira admits it's working on a hotfix for a Windows 7 Check Disk bug - and claims other security firms are affected

Antivirus firm Avira has admitted it's working on a fix for a mysterious Windows 7 bug that prompts the Check Disk utility to run at every start-up.

We reported earlier this month how the chkdsk bug refused to go away, having first reared its ugly head in the beta version of the operating system released earlier this year.

The glitch sees chkdsk report a potential error on the PC's hard disk, before reporting a clean bill of health once it's completed a scan. The only way to prevent the chkdsk screen running on start-up is to disable the utility.

Microsoft has remained mysteriously quiet about the issue, but several of the readers who commented on the PC Pro blogs and internet forums linked the bug to Avira antivirus software.

Now the company admits that it and other antivirus providers may have a problem. "As far as we can tell from the current state of investigation, the problem occurs in special conditions, when an operation is performed upon an already deleted file," Avira's technical editor, Dirk Knop, reports on the Avira TechBlog.

"This leads to the situation that the NTFS driver/the windows 7 kernel deems the file system as corrupted (which it is not) and sets the dirty-flag of the NTFS partition. This in turn leads to the chkdsk-run on the next start of the system. In previous versions of the windows kernel, the operating system just returned an error."

Avira adds that it should issue a hotfix for the problem this week, although it warns that "many other antivirus products seem to trigger this behaviour occasionally too, as we learned during the investigation of the problem".

Knop adds that Microsoft itself may be forced to address the issue with a Windows Update.

(Thanks to PC Pro reader Exlons for the tip-off.)

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