Is he running xp ?
If he is he will need the 'special' dell xp install cd that comes with the Pc. This should reboot the pc back to its original state (maybe even keeping his settings and files).
Dell are a nightmare ... Yes you get a good deal but you cannot upgrade them easily and If something go's wrong if you do not subscribe to their overated service plan or know what you are doing with PC's you get ripped off.
Any probs please ask me and I will find the answer out as soon as
May be I need to be hit with a large bat hehe 