Possible CPU cooling issue

Hi All,

I had a issue yesterday with my pc when I was in the middle of playing a game. The machine completely crashed and the display showed horizontal grey lines. I force powered the machine off, when I restarted the machine it failed to boot, there was no image on the display and the were 6 beeping noises coming from the motherboard/CPU. There would be 3 beeps at one tone and then 3 beeps at a higher tone and it would repeat. After a quick google this appeared to be a CPU cooling issue. I removed the CPU cooler (standard stock cooler) and cleaned it out but there was very little dust and the thermal paste was still intact. I tried to boot the machine up again still with no success. After leaving the pc for around 20 minutes it finally booted up and has been running with no problems, I've been monitoring the CPU temprature and they have been within the normal range. Talking to a friend today they mentioned they had a similar issue but it was there PSU. I haven't got a testing kit for my PSU currently but I am trying to get one in the next few days. Just wondering if anyone has any ideas?

Thanks for the help