Unlock Malcom,

Lauren and Brock the EASY way
Warining: This cheat involves editing the contents of your ut2003.ini file. Improper editing could cause the game to stop functioning properly. It is best to create a backup file before you perform this cheat.
Add the following lines into your ut2003.ini file:

[XInterface.Tab_PlayerSettings]
bUnlocked=True
bTDMUnlocked=True
bDOMUnlocked=True
bCTFUnlocked=True
bBRUnlocked=True