If the original error you were getting is referring to config.nt or autoexec.nt, you can try this to fix the problem.
1. Go to the Windows\System32 folder, and rename the files autoexec.nt and config.nt to autoexec.nt.old and config.nt.old, respectively (if you can't find one or both of the files, don't worry about it - this is probably what is causing the error in the first place).
2. Go to the Windows\Repair folder, and copy (not move) the autoexec.nt and config.nt files there to Windows\System32.
3. Kind of an extra step, but it doesn't hurt - set the config.nt and autoexec.nt files now in Windows\System32 to read-only. (right-click the file, left-click Properties on the menu. From the window, put a check in "Read-Only", and click OK.)
4. Now the easy step - reboot. =P (This'll probably fix that error where the installer is already in use, too.)
5. Try out the game again.
Can't take credit for any of this, really - most of it's here , but it's easier getting the files from the hard drive than the CD.
Hope this helps out some.
