Hi, hopefully someone will be able to help! When I play Call of Duty 4 or Battlefield Bad Company 2 my computer will randomly freeze. The screen will freeze and the sound will lock up and the only way to restore the computer is via a hard reset. I can play other games such as Crysis and Oblivion without ever having a problem. I dont recall this problem ever happening in single play mode only when online but I dont really play the games in single player mode that much. I have had the problem before with COD4/5 and never been able to fix it, I just lost interest in playing the games. With these games I have tried all the usual reinstalls and formats.... I thought it was the graphics card over heating but I have installed Rivatuner and it now never gets over 65-70c under load. So I have ruled that out. Now i think that is might be either bad RAM or my PSU not being powerful enough. The computer is stable and never crashes when I am not playing games, so am I right in thinking it is more likely to be the PSU than the RAM? I also upgraded the BIOS last night and managed to play for an hour and half until the system locked up again. Ok to the specs: I have a DELL XPS 420 Running Windows 7 64bit Windows: Microsoft Windows 7 6.1.7600 Memory (RAM): 3070 MB (came with the system) CPU Info: Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz CPU Speed: 2389.6 MHz Sound card: Speakers (High Definition Audio) Realtek Display Adapters: NVIDIA GeForce 8800 GT Network: Network Present Network Adapters: Intel(R) 82566DC-2 Gigabit Network Connection CD / DVD Drives: F: Optiarc DVD+-RW AD-5170S Manufacturer: Dell Inc. Product Make: Dell XPS420 AC Power Status: OnLine Time Zone: GMT Standard Time Battery: No Battery Motherboard: Dell Inc. 0TP406 PSU: Dell KH624 375W, +5v max 22a, -12c max 1a, 3.3v max 17a, +12v max 18a Most of the computer is the same as from the factory but I have added another Sata hdd and I have an external USB seagate harddrive too which has its own power lead. I also have a few extra USB devices such as webcam. Could these extra HDD be using too much power? Any ideas?