I have been experiencing an error known as
"VER_IRQL_NOT_LESS_OR_EQUAL" and according to the reboot error report, the following is involved:
C:\DOCUME~1\MICHAE~1\LOCALS~1\Temp\WER633e.dir00\Mini081409-01.dmp and C:\DOCUME~1\MICHAE~1\LOCALS~1\Temp\WER633e.dir00\sysdata.xml. Under my Event Viewer, I noticed an error stating that the boot-start or system-start driver known as Beep failed to load. I uninstalled Beep, but I couldn't figure out how to reinstall it. After uninstalling it, the error occured again about an hour later, and now I see this message under my Event Viewer: The file system structure on the disk is corrupt and unusable. Please run the chkdsk utility on the volume C:. Under my Event Viewer, I also see some system error codes. My system restore points are too recent to be of use, so I don't know what I should do. I did find a forum with help on a problem that appears to be the same (see http://www.computing.net/answers/windows-xp/xp-serious-error-on-bootup-sysdataxml/8407.html), but the advice there is conflicting so I don't know what I should do next.