High CPU fan speed after PSU change-out

Assuming the cpu fan is plugged in correctly, if it has a thermal controller function, that could be faulty.

check your tempretures to see if you knocked the cpu heatsink installing the psu

The temps before the replacement were around 35c. They haven't changed. I watched as my cousin did the change and I didn't notice anything out of the ordinary. One thing that I was wondering is, if he has 3 case fans all blowing out, one of them being on the side right above the CPU, would that fan interfere with the CPU fan and cause the CPU fan to push harder to make up for the loss in air flow? Sounds kinda iffy but was worth a shot on asking.

Typically I would say such a side fan should be blowing in....its a simple matter to turn it around and see what happens to the temps. Otherwise I would have to day Dai is correct and you will have to clean off the old thermal compound under the cpu heatsink and reapply some new.

Actually, I take back what I said. Everest was saying the wrong thing. It was saying that the CPU was at 6000rpm, and the System fan at 3000rpm. This is wrong. We conducted an little test and slowed down the fan of the CPU with our finger ever slightly to see a change. The 3000rpm went down only slightly. We couldn't figure out which it was that was at 6000rpm until we slowed the northbridge fan and the rpm went down. So, the northbridge fan was running at 6200rpm. Is this bad? Should he get an aftermarket heatsink without a fan?

such small fans need high rpm's i wouldnt mess with it, unless you get the idea its too hot, in that case mess with the direction of air travel in the case unitl you get the optimal air flow. often times fan can fight each other if you are not careful.

There's no problem with the 6,000RPM fan. One of mine runs at 5,400RPM due to its small size to achieve a decent air flow. Just moderate the temps as they'll show you whats wrong anywhere, and if you see anything going wrong there, then try as advised above or post back. It could be that the northbridge is heating up too much and thats making the fan speed up to such speeds.

The temps in the case are actually below average. None of the temps rarely get above 40c. I have found out what it actually might be, and that's the 120mm fan that was installed along with the power supply. That fan is as follows:

http://www.newegg.com/Product/Product.asp?Item=N82E16811999127

It is much louder than advertised (about 30-40db rather than 21), quite possibly due to it higher than advertised rpm (~3500rpm rather than 2000rpm). Is there something that can be done to drop that rpm down?

You may want to slow the fan doen to a more reasonable level. You can use the Zalman ZM-MC1 or if your mobo has any controllable fan headers a 4 to 3 pin adaptor and allow the mobo's bios to control the fan (if it supports such function)