High Pitched Fan Whine?

[arcticap]

My computer started producing a high pitched whine that sounds like a fan is stuck on extra high. Now I notice that the CPU temperature is affected and is running higher. At first I thought that maybe the old video card fan was maybe stuck because I first noticed it after watching some music videos. But it's not going off. Could it be the old OEM stock CPU heatsink or could it be the old video card?
When the MB and new CPU were recently replaced, I was told that it wasn't necessary to replace the OEM heatsink which came with the old CPU, even though I wanted to change have it replaced with something better. They said they didn't have anything else on hand.
Any suggestions? It sounds really annoying and I don't go into the case to work on it at all.
Do the regular fans start producing a high pitched whining sound when they start to go?

 

[Peter.Cort]

well, if you can, go into the case and just slowly stop each fan for only a fraction of a second, and if it stops, then that fan is out.

 

[arcticap]

Thanks.
I istalled programs & did a lot of temp. & fan rpm monitoring and it was such a hot, humid weekend that I wouldn't have thought that the 15 - 20 F. hotter air temperature could raise the CPU operating temp. by 5+ degrees C. and cause the CPU fan to whine. And that's with 4 case fans running.
It sounds like a vacuum cleaner once it gets going. Then there was a severe thunderstorm and the lower air temp. brought the CPU temp. down 5 C. and it's running somewhat quieter.
I should have insisted on a quieter CPU fan. I guess I just need to get used to the noise of summer operation. CPU normally runs at 40 C. and it's stable.