Cheapest things first.
If you can't get it running, I'd first try reformatting the harddrive and reinstalling Windows on it (unless you have some very important data on it and want to invest into getting it saved).
I've had a disk crash on me like this and it was probably just the file table (the thing that remembers where files on your disk are) messed up. Also you might want to bring your harddrive to some friend and try if you can get anything out of it in the usual way - just connect it to another computer as a second hdd.
If format&reinstall doesn't do the job and you're reasonably sure it's the hdd, why dump the whole computer? Just replace the harddrive, they're incredibly cheap these days.