Well that doesn't sound good, because as we all know bad blocks aren't good. But it must be some pretty non crucial file or you'd be seeing that happen more often (I think).
I'd do something like a full chkdsk, where you right click on the drive and go to properties, then tools, then check disk or whatever and tick those 2 boxes that indicate a more thourough scan (doing this from what I can remember). Then you need to reboot, and it takes forever to scan everything. But I believe in theory that scans all parts of your disk and marks bad areas as unusable to Windows. So that Windows doesn't attempt to write there.
I'm sure you knew all this.
Anyway thats what I'd do, and I'd probably start making backups just incase something real bad is about to happen.
There is a program called HDDRegenerator or HDDRegen.exe that can actually fix bad sectors if you are lucky and actually don't have a failing hd. In fact, if you can get ahold of that, it might be better to run that first rather than the full chkdsk.
