The Microsoft Download Center SafeDisc Windows XP Fix for Microsoft Games page contains the following overview:
When running a restricted user account with fast user switching under Windows XP, some games will not start correctly. The game requests that the original disk be placed in the drive, even if it is already present. To remedy this issue, download and run this fix.
This software will not alter or patch any component on your system, it will only change the startup state of the system component needed to start your game from start on demand (on game load), to start at boot (on Windows XP start).