iMac overheating? and fan speed issues

Hello,

It's my first post on this forum so please be kind!

I have a 24" iMac from 2007 (2.8GHz) which I'm pleased has lasted so long, but I have been noticing, more and more, that the fan speeds are quite high and in the end it makes my iMac quite noisy.

iStat pro tells me that the fan speeds are:

CPU: 1822rpm
Hard Drive: 2317rpm
Optical Drive: 833rpm

What's even more worrying is the temperatures (all in Celcius):

HD: 60
CPU: 54
Airport 63
Ambient: 27
GPU: 62
GPU Diode: 67
GPU Heatsink: 62
HD Bay 58

From reading around I've learned that HD temperature should be about 40 (C) and in general all these temperature should be MUCH lower, so I'm a little concerned about the health and future longevity of my iMac.

Does anyone have any suggestions as to what I can do? I have the tools to open the back up and remove any dust if there is any, but I've never done that before (the only change I've ever made was to add some more RAM about 2 years ago) and would prefer to take as little drastic action as necessary!

Thanks

Thanks for replying so quickly simsaladimbamba.

In terms of CPU usage in the Activity Monitor, nothing seems unusually high. Google chrome occasionally pops up to about 15%, as does my HDD backup software, but otherwise everything's fine when the iMac's not doing much (mostly using 0.0%, with a few 1-2%s).

Looking at the instructions for resetting the SMC, from what I understood it looks like all you have to do is remove the power supply for about 15 seconds - if that's the case then the last time I reset the SMC was about 2 months ago when I had the computer off and unplugged for about a week. The fan speeds have definitely been high for quite a while longer than that though.

Thanks for the encouraging comments about the temperatures though - it's good to know that it's not running too hot!