hi there, anyone i need your help. i have successfully installed command and conquer generals zero hour with my vista. but the problem is whenever i try to play solo it always says that there is a missing cd and i need to insert it. anyone please HELP!!!!

My Computer
System One
-
- Manufacturer/Model
- hp cq50
- CPU
- amd athlon dual core ql-60
- Memory
- 1790 mb
- Graphics card(s)
- nvidia ge force 8200m g
- Monitor(s) Displays
- ganeric pnp monitor
- Screen Resolution
- 1280x800