Ok so heres my problem, this is my first build on my own and it has ran fine for probably 6 months. i have an asus p5k pro mobo, 4 gigs of corsair 6400 ram, raptor 160hdd, 800psu, crossfired 3870s, and a q6600 processor in an antec 900 gaming case. i upgraded to vista ultimate a few days ago and i was a little unsure for awhile but now im loving it, the problem is that when i came home from work tonight and started my comp up it ran no overclocking check and just started right up. i had no video input on my screen and i checked my cables and nothing, i restarted the system and it came up and didnt do the oc check again and then told me that oc had failed and asked if i wanted to enter setup or load defaults i tinkered in setup with no luck. i had overclocked everything to start with by bumping up the fsb and then turning up the voltage and changing the frequency of the processor. i had it ocd from 2.4ghz to 3.4ghz and it was running at 17c idle and 28c load. it still shows in ai suite that its ocd and the fsb is ocd but the ram i changed the timings on in bios and i dont remember exactly to what but they reverted back to normal. my hdd sounds really bad to on startup as well like its struggling to get going. so heres my question after all of that, why isnt it doing the oc check anymore and why did it become unstable all of the sudden. should i update my bios or flash the hdd and do a from scratch install?

You need to be more specific about your power supply (800W means nothing)...also need more details on how you went about overclocking. The Q6600 defaults are 9 x 266MHz. To get it up to 3.4GHz, did you simply jack up the CPU freq to about 375MHz or did you reclock the CPU to 8.5 x 400MHz? And what did you do with the RAM freq when you jacked up the CPU? Hopefully you manually overclocked thru the BIOS & didn't use AI? Your temps seem out of whack. 17C at idle? That's pretty darn low, well below room temperature. What type of cooling are you using? or do you live in an igloo? lol

Did you lock the pci bus? You make have damaged your hard drive by overclocking the bus itself. You should go to the bios and load the defaults and see if you can boot. If you can boot go back to the bios and tweak the settings as defaults are not optimal.

yeah 8.5 x 400 and yes ram overclocking was done in bios. my room is really cold but my friend said my temp is really low too but thats what it says in the ai suite. rosewill rcx z4 fan. i restarted my comp again and went into bios and redid the ram timings back to where they were and it started up fine no problems. but it still wont do the oc check when it starts up.

I wouldn't trust ai suite-it's known to soemtimes give too low a temperature. Check the cpu temperature in the bios and compare.

people talk about "tweaking" and "optimizing" BIOS settings here a lot. But if your mobo was manufactured in the last decade or so, you should at minimum be able to post and boot to os from default bios settings. i usually recommend STARTING at default settings, and THEN tweaking/optimizing. I especially recommend reverting back to defaults when people have been messing with BIOS settings and report "i changed the timings on in bios and i dont remember exactly to what..."

im not totally sure what happened the first time it started and messed up, i have everything back to the way it was and running in prime 95, i downloaded core temp and at 3.4ghz processor is at about 60c under load. i put all the settings back to the way they were before hand and its all running smoothly no prob but i just cant figure out why that happened in the first place after running stable for so long. would upgrading to vista have anything to do with it?