Shoutbox

I am using os-windows xp pro and my pc randomley freezes. This will happen when I click on a system tray icon, nothing happens and then freezing begins. I try to use task manager to end the offending programs but it too will then freeze and the screen will go strange. Sometimes things will return to normal if I leave the pc for 10 mins or so. Also IE sometimes becomes non responsive, web pages won't load and my internet connection stops, even though I have high speed cable broadband which is reliable, it's definitely the pc. Programs just keep freezing and NOTHING responds so I am forced to unplug the dam thing and switch it back on; then it just works like nothing had ever happened, until the next time. I have run disk defrag, disk check, I have 50% free space on my hard drive. I have run MS memory checker, all no problems detected. I run Adware , so no spyware. I have anti virus software that I run everyday, so no virus infection. I have a software firewall installed. I even run Registry Mechanic, it finds no problems apart from deleted windows media player registry values and stuff. Windows xp tells me all my devices are working properly and there are no conflicts. I have run an online test @ PcPitstop, again no problems detected. I have no doggy software on my pc and there are no strange or unneccesary processes running. I have re-installed windows xp pro, this did not resolve the problem. Everything should be hunky dorey, but it's not. The dam thing keeps freezing for no apparant reason! Can anyone please give me any advice to help me solve this problem?