so there's a 50-50 chance that this will work. Its sort of a problem with a lot of XP games that they expect to have administrator rights. You can try uninstalling it from your account and re-installing it in his. Microsoft itself has put out a support bulletin -- http://support.microsoft.com/kb/893677

Basically they say that older games require administrative privs, and you can do that for a specific game without opening up the whole account. they provide instructions on the bulletin.