HELP !! Laptop troubles !!

hi there all...major problem here with laptop...using Windows 2000 Professional with NT Workstation 4.0. Problem - On initial bootup, I get a "lsass.exe - Entry Point Not Found" message. Also says "C:/WINNT/System32/lsass.exe terminated unexpectedly with status code 128. HELP !! I can't even get into my computer !!! Would reinstalling Windows 2000 correct everything? I deleted some Windows HOT FIX files that have apparently screwed up my entire system !! HELP or suggestions ?!?! Thanks !!