Screen freeze/lockup on dell dimension e520
Every time i run too many applications, like a game such as league of legends or something, itunes, and skype, (thats not alot), my computer just completely freezes.(Not a blue screen just freezes the screen and i can't move the mouse, or do anything). The keyboard lights(num lock caps lock, scroll lock) turn off. Everything else in my computer stays on. I ran the Dell PC diagnostics and it passed everything. I bought more ram, a better processor, and a better graphics card, but it still crashes. I tried reinstalling windows xp, and reformatting my computer, but it didnt help. I switched the Sata cables from 1 and 2 to 4 and 5. I downloaded the latest drivers for my computer on the dell website. I don't know what to do. Could it be my hard drive, or motherboard causing these crashes? If you have any questions about my computer please ask. Please Help. Thanks!