AvP 2 single player problem

A friend of mine has this problem: when he tries to launch single player, the game sends him back to the menu, I searched and I found some people with the same problem, but not solutions. His game is set in Low graphics , but he fits the recommended requeriments (he has 256mb of RAM, 32mb video card, and at least 1.5gb free in his hard drive). Although he is a fan, he has never played an AvP game, I thought he would be able to play avp2 at least :/
Does anyone know to solve it?

Thank you.

Sounds like this might be solution: Turn off his anti-virus software. There is a .dll file avp2 single player uses that most anti-virus programs think is a real virus. Just turn the AV off while wanting to play singleplayer