I'm happy to say that I've only had this happen to me once before: Windows really, really won't boot. You can't even get to safe mode. All you get is "Windows NT could not start because the below file is missing or corrupt" and a prompt to reboot over and over again. This usually seems like a reinstall moment (especially if you ask tech support), but it doesn't have to be so: Short-Media is running a guide called Repairing Windows XP in Eight Commands
. The trick is getting into the Windows Recovery Console (which requires your XP install disc), rebuilding Windows' boot files, running CHKDSK, and fixing the boot sector. It may sound complex, but it really is just eight commands. However, be sure to read the whole article to avoid a few common gotchas.