I just purchased Call of Duty and United Offensive. I have Windows 7 on my desktop. After installing them one at a time (Call of Duty first) with anti-virus off, both of them refuse to start single player. I don't get any error messages...they just will not start. I am careful to make sure that CD 1 of the correct game is in the CD drive but it does not help. I can start multi-player for both of them but when I select the Single Player option from the multi-player menu, the game just goes away as if I had selected Exit.
Call of Duty 2 has worked beautifully on my computer for some years but Call of Duty and United Offensive will not.
I do not have a clue what to try next.