New computer having startup problems

[SevenSacredSins]

Ok recently I built a new computer as listed in my signature and everything has been perfect for a few weeks. I recently tidied up the case a little, I just tied together a case fan 4-pin connector with the CPU fan connector to keep it off my 5870. Now I seem to have start up problems, I boot it up and the resolution is 640 x 480 then it goes to the blue screen saying the system has failed, it then reboots and fails again and finally after rebooting itself again it works. I've been having this problem for a few days now, it seems to happen if I leave it off for around 10-12 hours, if I just turn it off for like 5-6 hours it works perfectly. Also when I do turn it on I hear rumbling from the case, it seems to be coming from the PSU or the HDD, not too sure actually. PSU seems fine, it's a 750HX and my system only uses around 500W but could that be the problem or that the HDD is faulty?

Please help, thanks

 

[shovenose]

i dont think its ur hard drive. try redoing all the connections (mobo, graphisc, etc,) and reseating the graphics and ram...

 

[SevenSacredSins]

I'll do that, might've disconnected something but everything works perfectly once I log in, CPU, GPU, RAM and HDD...strange