OK I am having to guess/assume a lot here, because you did not give us details.

1. Unless you have a very strange way of using a computer I guess that your hand/mouse are faily close to it, so it must be on your desktop/work unit, and not on the floor? I assume you are feeling warm air?..............if it is radiant heat I would say your box is just about to fry

2. If hot air is the case, it sounds like you have a front mounted fan(s). In which case it/they is/are mounted wrong way round?...fans at the front should suck air IN. This is particularly true if their job is to cool the hard drive. They should take air in, to be exhausted at the back.

3. Try an exhaust fan (about $5). It will take up a PCI slot but will clear 40-60 cfm of air out the back.

4. Make sure that there is at least 12" between the box and the wall........24" would be better.

5. If you don't want to fry your HDD a special mounting with fans is an idea........I guess they are around $10?

6. Tidy up the cables with those little ties, and make sure that the flat ones are not impeding airflow.

Cheers

EDIT...........guess I type rather slooooooooooooooooowwwwwwwwwwwwww?

Could the heat be hot air blowing back from the wall behind your base unit?