Well guys this has been a problem of mine since I started playing COD4. Basically what happens to me is that I try to play in a modded server and sometimes the game will crash, i'm sure this has happened to everyone before. My unique experience was when I tried to go back into the game the screen went black and there was no way to fix it other than restoring the computer to an earlier time period. This was getting annoying and would happen multiple times a day on bad days. So i've found the answer First what you want to do is click start ---> My computer ---> Local Disk(C:) ---> Program Files ---> Activision ---> Call of Duty 4 - Modern Warfare ---> Players ---> Profiles ---> Your profile---> config_mp file---> Right click ---> Properties---> Look at the bottom in Attributes click "read-only" ---> Apply ---> OK, Congrats your problems are over!
Thanks Redrock for the help.