iMac overheating please help

[macroom2]

My iMac is overheating and i read an article on "macworld.co.uk" which instruct to change the minimum fan speed of the CPU to 2800 rpm and the Hard Drive to 2200 rpm using a software called "smcFancontrol"
i have installed the application and here's a screen shot from my iMac instating that the current min speed for CPU is 940rpm! and for Hard drive is 1100rpm:

Please advice me about this, is it safe to change the min to 2800 and 2200rpm or it would damage my iMac?

Thanks in advance,,

 

[tubeexperience]

The proper thing to do is to clean out dust and apply new thermal paste.

 

[cynics]

Increasing the fan speed won't hurt anything.

However what is overheating? What temps are you seeing?