I don't think that would work for Shlup's problem though

You could create a new Administrator account, and see if it's fixed in there. If it is, then yes, it's a policy problem as Baloki was trying to hint towards but not say very clearly. Yes, it's possible that a virus has gone and changed those policy settings for you, so get rid of it first

If you have XP Pro though, don't bother get Poledit, since that's replaced by the Group Policy Editor, which you can access by going to Start > Run and typing "gpedit.msc".