Try repeatedly pressing F8 while booting - or possibly F2. Do you not even get the pre-boot screen? If not, try interrupting the boot sequence by holding the power button down until it powers off, while it sounds like it's booting. Hopefully, then, next time you start it, you'll get the options to start in Normal Mode, Safe Mode, Safe Mode with Networking, etc. Choose Safe Mode, then see if you can access System Restore. If you can't even get into safe mode, then it sounds pretty terminal. Have you got a Windows CD you could boot from? Alternatively, you could try a Linux Live CD, which might have some success. Sam would be the best one to advise on that.