Ricardo :

Maybe you cant resolve your problem to reinstall Windows 2000. Sometimes the system kernel damage with a "extra" software instalation like mail server. This procedure should recovery the lost partition. I had similar problem 2 months ago and it resolved my problem. You must know that Windows 2000 has differents problems.You need to install Windows 2000 with CD-ROM (boot from there).

Its a little colaboration to resolve your problem. I hope that you will can resolve it.

Eng. Miguel Ortiz