Recently had very similar problems with my nephew's computer.
As has been mentioned, check your video card drivers.
Make sure you have the most current version of them.
If you already have the most current version of them, go back to the previous version as has already been mentioned.
As far as your front USB ports are concerned, it may be a USB driver problem (check your the CD that comes with the motherboard for them!) OR it may be a case of 'loose' wiring.
Front USB ports are normally a 'plug in' unit that comes from a set of pins at/near the front edge of the motherboard, while the rear USB ports are 'hardwired' directly to the motherboard itself.
Don't worry too much about the power supply.
If it was the power supply, other things would be going wrong a long time before the USB ports would start giving problems and *all* of them would be doing it at the same time.
As far as XP being strange if the install is over a year old, bleh to that. I had an XP install for over over 3 years and it ran fine, until I messed it up. *sigh*
Re-installing XP is a last ditch fix as far as I am concerned, only do it if nothing else works and then make sure that you have all of the drivers for the motherboard and other cards before you even think of doing that or it will cause more problems than it is worth.
So far "Primitve" has given the best 'help' so far I reckon. Asked good questions in order to get more info to help.
The more info on your system that you provide, the easier it is to get the RIGHT answers to sort your problem. :cool: