I use Memtest86+, Prime95, and IntelBurnTest. In that order, I put IBT last because I trust it less, I test overclocks and it doesn't find anything wrong for hours and hours and hours but Prime95 took under and hour to find something wrong. You can also browse the web and watch videos or whatever while Prime95 is running, if your system is unstable then it might manifest as something like browser crashes or a BSOD (don't do anything important). Unless you have reason to believe your GPU is defective I'd put that last, play a game or something.
thanks everyone for the programs you posted......i have a question though....i stress test the the GPUs( i have crossfire) and although i see them both in the program only the main one loads .....the other GPU`s load is zero and temprature normal. can anyone explain why? should this happen or the load should be divided to both cards?
i found oute what was going on after a lot of digging....................simply crossfire does not work on window mode so when i was running furmark in window mode only the main GPU was active but when i run it in fullscreen the other one "wakes up"...... lol ..........i wonder why this happens though