Yesterday my PC started emitting some annoying and high pitched noise, that made me think that the fan was working like crazy, then I started to get this weird messages from programs not responding, etc, could this be a sign of overheating??? I opened my box but found everything looked the same. What is the proper way to detect a fan failure?
System specs:
Dell dimension 8200
winxp pro
256 ram

Haven't altered the cooling system in any way, my box has been working great for 1.5-2 yrs, never had a problem like this on any PC I've owned so I don't know how to replace a fan/cooling system. If you think this is needed please point my in the right direction to do it properly.

thanks
J