After my upgrade to Windows 7 from Vista, I see thisevent reported regularly in my System log: eventid 55, "The file system structure on the disk is corrupt and unusable. Please run the chkdsk utility on the volume Win7OS". The latter is my active system partition.This is what I did to try toresolve the issue:ran chkdsk which did not report any errors;ran "chkdsk /F /R" to resolve the issue;ran "fsutil dirty query c:" but the active partion is not dirty;ran PerfectDisk, no MFT fragmentation;checked my harddisk SMART properties, but no issues found.However, it eventid 55 goes away for a few days and returns again.There are 4096 bytes in each allocation unit, so not too many small allocation units, I guess.I looked on the net for answers, but I did not find any that makes sense to me. Is it related to my Avira app?Is it related to my Raxco PerfectDisk 10 app?Is it related to my Acronis TrueImage Home 2010 app?Is it an issue in Windows 7?This issue occurs on an Asus notebook bought in June this year and with the info I have now, I suspect the issue is related to a logical error rather than a physical one.What option is left to make the error go away before it becomes worse? Would format C: be an option and then install e.g. Acronis image on the partition? Do I need to worry and do a low level surface check on the harddisk?Thanks for sharing your thoughts.David

This kind of issues can be caused by incompatible ATA\IDE controller drivers or the drivers for your hard disks. I suggest you upgrade the BIOS, chipset drivers and SATA drivers from ASUS website. ASUSTeK Computer Inc.-Support- Important Note: Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information. If the latest drivers do not help, please contact ASUS to ask if your disks are compatible with Windows 7. ASUS North America SupportArthur Xie - MSFT

I've been getting the identical symptoms on my machine for the past few days, repeating about twice a day. However, I ran the Beta and RC1 versions of Win 7 for months without any such problem, and then the RTM for several weeks before the problem occurred, so I don't think it's to do with the BIOS. I wonder if there's a rogue update among the recent batch.

Could be another case of http://social.technet.microsoft.com/Forums/en/w7itprogeneral/thread/df935a52-a0a9-4f67-ac82-bc39e0585148 (http://tinyurl.com/w7corrupt)We see this error reported for our application at least a few times per day. Exclusively on Windows 7.