CPU fan has failed, Service PC immediately to prevent damage to cpu

Since we're dealing with the AM3 platform, I take it you're on a desktop system, if so first of all you'll have to remove the side panel on your machine by unscrewing it and sliding it towards the back of the case, it will come out easily. Then make sure that:

• the CPU fan power cable is connected to the motherboard (likewise, on water cooling systems all cables should be properly plugged in)
• the fan is not clogged with dust or any objects preventing it from spinning

Try to turn it on again, if you're still getting the error message, but with the case open you can see the fan is running fine, you should check the CPU fan speed from the BIOS and ensure your cooler meets the heat dissipation requirements of your CPU.

In case the fan is not spinning, immediately shut down the machine and just follow this guide to remove and replace the fan (step 6) while giving the cooler a good clean in the process.