Right-click on my computer, choose properties then the auto update tab. That is for XP, think it is the same in 2000
If that doesn't help try deleting winuptmgr.exe and wuauclt.exe from the system32 dir and the drivercache dir while in safe mode, this should make windowsupdate download new updated windows update files. Helped me once to get it working again
Hope you get it sorted