Ok I did that yesterday and it went fine, I could play GTA 4 for an hour, and another game after that for 30 minutes without any errors. I thought that overheating was the cause.
Today, I tried again, booting up, 1 minute after boot: IRQL_NOT_LESS_OR_EQUAL (with the case open and the fan next to it). Restarted, tried GTA 4 again, ran for around 12 minutes I think, then again IRQL_NOT_LESS_OR_EQUAL. Although this time the cpu heat showed up to 53 degree celsius with the fan. I'm not sure if the cooling just didn't work as well as before (but I think it did, its a huge fan after all) or if this is just the old problem again.
Question is: Why did it work for so long yesterday, even after shutting down and after 30 minutes trying again? If it were a one-time-luck thing why did it work twice?
Edit: Did another try. I moved all cables out of the way that could hinder the external fan, and it ran GTA 4 for 60 minutes until I closed it. Then, a second after I closed it, restart, without a bluescreen and without an error message at the next start.The CPU gets around 50 degree celsius with external fan and case opened. Isn't that pretty hot? I read that IRQL_NOT_LESS_OR_EQUAL is most of the time either bad ram or overheating CPU, so I thought this was likely.
Do you think that that could be the case too? Should I get another CPU fan, change it and see how it works then? I touched the heatsink and its not even "warm", its almost totally cool. That isn't right, is it? With the CPU being 30-50 degree, the heatsink shouldn't be cold right? I really hope this is the problem and not something else.