Laptop won't boot

I have an old IBM Thinkpad 600E. I revently installed Windows 2000 Pro and it was running great. It started shutting down while I was using it. When I re-started it, I would get an error message that files were missing. Now it won't even boot, it stays on th IBM Thinkpad screen. I don't want to put much money into it since it is quite old, but it was good for my needs. Any suggestions as to why it will not boot?