User Accounts

Trying to set up a user account for my son on my PC but having lots of
trouble.. once I have his account set up it runs real slowly and I can't
change the Performance Options to 'best performance'.. neither can I change
it to 'Windows Classic Style' in Display Properties.. also: got a message
early on in the process User Environment.. "Windows cannot load the
user's profile but has logged you into default profile. Cannot find the file
specified." Also: having an error message visual styles.. could not load
visual styles because the file failed to load.
Any help would be greatly appreciated.
Rob