Perhaps you can try to rewrite the MBR file. If you have some Windows repair disc around, I believe you can find some option on that for "fixing boot problems" or something of that nature. You shouldn't have a problem booting to compact disk if you have a disc reader. If not, I would install an iso of a modern Linux distro installer (such as
Mint or
Ubuntu) or
boot-repair-disc to a flash drive. If you boot in to a distro installer, you will have to manually install and run yannubuntu's
boot-repair utility, which can repair an MBR file. Likewise, boot-repair-disc should do this too, though I have yet to try it myself. Hopefully you will be able to boot into something!
EDIT
Almost forgot another option! If you have another personal computer around and a means of running the system hard drive of your problematic computer on that other personal computer, then you can usually rewrite the MBR file of the problem PC's drive with partition management software (like
Partition Master)