if you have a win2k disc try this
1. Start the computer by using the Windows 2000 compact disc (CD-ROM).
2. At the Welcome to Setup menu, press R.
3. Press R to select the emergency repair process.
4. Press M to select Manual Repair.
5. Press ENTER to perform the selected tasks.
6. Follow the remaining instructions to repair the Windows 2000 installation.
7. Obtain and install the field patch for the McAfee GroupShield Exchange program from McAfee.
this from
here