MAD's Weapon Mod works on XP - for all XP users, you must do the following:

1. Update your .NetFramework to v3.5 - (as previously stated by MAD)
2. Update your PC/Laptop's Service Pack to SP3
3. Reboot PC/Laptop
4. Ensure that both the Weapon.exe file and the Weapon.mdb file are on the root of the c:\ in the same folder
5. Double click the .exe file and BOOM - your creativity is unleashed to generate an unbelievable array of endless codes

Thanks again to MAD Industries & Zack_Strife

Best,
Four20 - "with some1" :G