Yeah so my Xbox has been overheating nearly every-time I've played it and don't know how to fix it. The power brick is relatively close to the system itself and both are off the ground. If you didn't know when it overheats it turns itself off to stop itself from breaking, that's kinda why I want to fix it. Also I am already aware of the Xbox fan and such but am looking for non costly alternative, I appreciate any advice you can give me :)

you can't fix it's broken.
anything you do will only buy you like a day before it breaks again.

@kingzetta: That's quite true about most Xbox's, I'll try and see how long it lasts.

I think the fan is kind of your only option.

What system version are we talking about here?

Is it enclosed in an entertainment centre? Might be worth moving it onto a shelf/desk so it's got plenty of room to 'breath'.

Remove the case, just run it as a mess of silicon and wires and shit.

All joking aside, are we talking original original? Like, big black thing? You can pick a new one for next to nothing at this point. Might be used but better than broken.

If all you're getting is overheating, and not RRoD, you can open it up and re-apply thermal paste to the heat-sinks. Before that you could look in the back vents and check for dust. If you see lots of dust open the disc drive and try to blow it out with some canned air (spray from the disc drive back, not inward from the exhaust vent). Another thing I've seen people do, but haven't done myself, is use a USB powered laptop fan like this. 
I wouldn't bother sending it to MS for repair. Last I saw they're charging $150 to fix 'em and a new 4GB is $200. If you take your old HDD out of its case it'll fit inside the new 360s'.

Install shit.. it'll be quieter and cooler, and a bit faster

Try to unload it on some poor sucker!

There's probably a load of dust in it, use a can of air and blow it out. My laptop gets dusty and then runs pretty hot too. You'd be surprised.

Or yeah, if you have assembled a computer before and it's still overheating, just watch a guide on youtube on how to take it apart and use arctic silver or something similar on the heatsink.