I have a few things here I'm they have been posted around here a few times, but I'm to compile them together for everyone.
1. Keygen for COD4- Simply run the keygen *will not work online only LAN/Network/Single player
2. NO-DVD Patch- This allows you to play single player without the DVD
Follow this path: C:\Program Files\Activision\Call of Duty 4 - Modern Warfare *then find the iw3sp file copy that on your desktop as a back up in case this does not work. Then open the DVD FIX and find iw3sp and replace that with your iw3sp located in your COD4 folder.
3. Level 55 hack- Again just run easyaccount.exe and select the patch that you are using then play a game to save your stats.
* I do not take any credit for these hacks *