CPU or PSU temperature 70-80+ degrees Celsius?

Question

BIOS is saying my CPU (AMD Barton 3000+, not overclocked) is running between the mid 60's (while idle) to 80+ degrees, but PC Wizard says it is the PSU that is running at that temp, while the CPU is around the mid twenties.

I would assume BIOS is correct, but why are the readings so different?

Here's a link to my PSU: http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=1030240&CatId=1077

About the high temperature, I recently applied thermal paste (we didn't apply it when we bought it 2+ years ago, but I would imagine it came with some on it) and it seemed to make a difference at first, but it's still obviously way too hot. I'm pretty sure it's been running at high temperatures since I got it, but it's been getting worse.
Also, when I put my hand by the fan of the PSU, it doesn't feel hot.

At this point, I'm not really sure what to do.

The PSU came with the case :/

It isn't dusty, as it was recently cleaned.

As far as I can tell, the airflow is fine.

Answer 1

I wouldn't advertise I owned that PSU if I were you. Did you remove the thermal pad from the heatsink before you applied the paste?

Answer 2

Firstly, check to make sure there is enough air flowing around the PSU, if the case is inside a closed cupboard or shelf, move it so it get enough cool air flow. Check the inside, incl around the PSU for dust, and give a good clean, also ensure rear, front and side vents are clear and get sufficient air flow.
One of the common killers of computers is lack of air flow and dust.
Cases with side mounted and extra rear mounted fans are ideal as they allow more air to flow over the internals.

Answer 3

Keep your PC away from any radiators. Better still, do what many people do including myself... remove the side cover of your PC to expose the insides of the machine