Many FPS Guides say that you should set the process priority in the taskmanager to "high". But always alt+tab'ing out of the game is kind of anoying.
So here is a better way - Set it permanently!
All you have to do is:
1. Create a .txt file and copy n' paste the following into it.
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\bf1.exe\PerfOptions]
2. Save the file as .reg
3. Run it - Done!
Hope you like it