Thanks for speedy responses.
In a nutshell:
-Account is an administrator account
-AV is off (but i think i might be able to make it "offer" in the task manager...)
-The games are a mixed bunch of old, new and demo games. All have been succesfully installed on at least one other system. Mine. The only game to succesfully install has been Vampire: Bloodlines. Others like Red Alert, Lego Indiana Jones, Thief 2 will not. If there's a fault pattern in teh games themselves, i can't see it. The machine is slightly newer than my own machine and running very similar hardware and software.
-Probably a silly question, before i ask, but Defender?...