I'll start with my specs: 3.2Ghz Pentium 4 Dual CPU 1280MB DDR RAM 240GB HDD 128MB Radeon X300 Now, as the title inclines, my computer likes to restart and/or completely lockdown, replaying the last milliseconds of sound for eternity until I pull the plug. It's usually during playing a game, especially one with a high system-toll, but some times it does it when I'm running Dreamweaver and Photoshop at the same time, both heavy system-toll programs. This situation is getting quite annoying; when I try to run the new Starship Troopers demo, my computer freezes just a few seconds into the game, and when I run the Age of Empires 3 demo, the system restarts before the game even opens! I thought this might have been a RAM problem, as on the rare case the computer would save itself from restarting, I would get a "memory cannot be read". My computer has four 256MB Infineon cards, so I replaced one with a 512MB Kingston card - and yet, half an hour into turning my computer on, it locks up when trying to open another program. So what are the usual culprits and what can I do to try and stop this happening? Thank you greatly for your help.