Got an APEVIA ATX-CB700W...plugged to a GIGABYTE GA-H67MA-USB3-B3 mobo, a Core i5-2400 (95W max. TDP), 4gigs RAM...PSU ran smooth since I bought it...lately I´ve added a Sapphire HD 6870 graphics card (max.151W TDP)...in first days went fine...last night started to make a little bit of noise....like a long beep each time i run Darksiders II THQ video presentation (when I first played it with the same PSU didn´t make that noise)...while in gameplay...quiets down...same happens with Blades of Time, while in presentation video, noisy, gameplay, quiet...when I close my ear to the PSU seems like it´s the fan (cause noise kinda has the same "rhythm" as the fan´s revolutions)...so...what it might be?...is it bad?..do I have to change it?
It could be a problem with the components in the PSU, not the fan. I had a PSU that started to make beeping noises when the computer was under load. One day it wouldn't work and I opened it up to find that almost all the caps had blown. I can't remember the brand, but it wasn't a cheap one.