Cant belive no ones asked this but in Control Panel -> Administrator Tools -> Event Viewer, take a look under system and applications and look for any red marks, though windows in freezing normally there is still logs of problems which happen before the freeze., report back and problems in their.
(This is always my first step with problems)
Need computer tech help badly (or I might kill myself)
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Thanks for the advice MadMunky, I'll check this out. But I am happy to announce that I have solved my problems (at least I think I have, haven't had a crash since yesterday afternoon). How did I do it ? Well I simply bought a new graphics card... 
Now I have a Powercolor Radeon 9600XT for sale... My new graphics card is an ASUS A9550 (also a Radeon, but less powerful) and it seems to be working perfectly (at least for CSBWindows !). Thanks everyone for all the useful information, I learnt many new things reading all your input.
Now I have a Powercolor Radeon 9600XT for sale... My new graphics card is an ASUS A9550 (also a Radeon, but less powerful) and it seems to be working perfectly (at least for CSBWindows !). Thanks everyone for all the useful information, I learnt many new things reading all your input.