How do you run an old game (that I think is Win 98 based) on an XP Operating system? When I run it normally it tells me that my system can't cope with the graphics which is mad as I have a pretty good PC. The game is aliens vs Predator by the way.
If you have a desktop icon right click on it, goto properties and its the third tab - compatability. If you read the link that Fruit Bat /\0/\ gave you it explains how to do it. In fact you said it still doesn't work so presumably you've tried it.