XP - Keeps clicking out of a screen

Afternoon all,

Seem to be having problems with my PC at the moment, awaiting XP discs from Dell (came preloaded but never got cd's)

Had a few problems booting up the system as it was hanging, held on the old mup.sys issue.

Back in again now, however when typing or on a screen of any kind (control panel or IE8 or Firefox) after a few keystrokes the active screen (argument sake blue when live and in use) suddenly goes grey and i have to click back onto it again to carry on typing.

This can go on for several minutes, sometimes it manages fine that has a mad few minutes.

I have SAS running, also AVG. Ran through the Malwarebytes anti-malware too.

Any help appreciated, will provides logs if needed (let me know which and how if not obvious lol)

Thanks all,

Vinny