A few months after i got my new Dell dimension 8400 it started going crazy every time i would play a game on it or just run a few big programs. I tried cleaning out the back and even opening the case and cleaning what i could but i can still see a lot of dust in there.. I wanted to know what could be some solutions and where i can find out the temperature/fan speeds

Try blowing out the insides with a can of air, if you blow through the fans try to place a something through them to keep the fans from spinning. This will protect the bearings of the fans and make it easier to blow through the blades.

There are several programs that will give you temperatures and fan speeds, Everest Home Edition will provide you with most any information that you could want.

The CPU fan we can take for granted that it will be monitored, but unless the case fan is connected to the motherboard by a three wire plug you will not be able to monitor its speed. Any fans that are connected by a molex connector will not be monitored either.

There are other programs out there, and I'm sure that there are members here who will attest to their favorites, but the accuracy of any of these is questionable. The method of sensing uses resistance and voltage to determine what is happening, all you need is a small voltage variance and the spec will be off. For temperatures, if it ain't shutting down...it ain't too hot.

my dell dimesntion 5150 does this - its a combo of a rattly case and dvd enclosure