FAN sounds like a mofo

i was playing americas army last night and ive had this pc for almost 2 months now custom build p4 2.4C, asus p4p800 dlx, seagate 120gig SATA, and also have two fans in my case, one is a antec 80mm (intake) blue fan and the other one came with the case id ont know what brand, usually my comp runs at like 25-30C both mobo and cpu idle and then when i play games for like 2h or so it doesnt go over 35C for both, well last night i was playing when all of a sudden this humming sound really loud starting coming from the case i thought ohh god there goes some part, then i put my ear to it and realized it was the other fan 92mm as (exhaust). so i was wondering what made the computer start make the fan spin all of a sudden so fast, usally that never happened and it happened today once again, i updated my bio unning 1.015 and i have the q-fan control thing enabled in my bios. any ideas why its doing that, cause it is pretty loud and irretating. thx in advance

it could be that the fan has an auto sensor or that the motherboard has and at a certain temp it picks up the speed to remove the hot air fron the case. It happened to me with some fans i bought not realising them had sensors and it sounded like a jumpjet powering up for VSTOL.

If your system maxxes out at 35° with just two fans then you've got some magic fans there...I wouldn't begrudge them a little noise now and then.

yea its very cool system i had it oced to 3ghz once with one fan in it, and i had some cpustree.exe thing running for like 30min and i had that open twice and my temp stayed at like 49C and it was full load, so i dont know i think thats good but then my friend told me im crazy and now im running 2.4ghz again

49 deg at load is not crazy

so ur saying it was good when i had it at 3ghz was running some cpustress.exe file twice on my pc and max was 49C?

Well, maybe not "good", but not fatal either.
I would consider staying below 40° at full load to be good.
Below 35° would be excellent.
Below 30° would be exceptional.