I have a PC with windows 7, and I'm experiencing random freezes with increasing frequency. After some time (from 30 minutes to a few hours) the screen will shows a random color or pattern (vertical lines) and nothing works anymore, I need to reboot manually.

I've checked the events log, but nothing is shown except for the unexpected reboot. I've tested the RAM with Memtest86+ 4.20, and the graphics card with FurMark 1.10.3, no errors have been found.

I've updated the graphic drivers and openned the case to remove dust, but the issue is still there.

Also, the problem doesn't seem to arise when I'm playing games fullscreen, but when I'm surfing the web, using itunes, or coding.

My hardware is as follows :

• intel core i5 750 CPU,
• ATI Radeon HD 5670 graphics card,
• ASUSTeK P7P55D motherboard,
• two 2Gb KINGSTON DDR3 ram sticks,
• 2 SATA hard drives,
• a Netgear dongle for wifi.