I assume you mean Dell's "Low profile" desktop? If you have one of these, the cooling fan is part of the power supply. It's pretty easy to change. I've swapped out a few. A word of advice if you do choose to go this route: order it new from Dell. It's only about $20 more than a refurb and it's guaranteed to work.
Another thing to consider that helps cool it down is to add a video card rather than use the on-board graphics. On-board graphics heats up the system because it's almost always doing something. If you get card, try to get one with it's own fan (hard to do in a "half-height card").
Kevin
Yes, it's streamlined, slimmer than a regular desktop. Overheating is a problem with the Dimension 4600C, not just mine. I've heard the same complaint with several 4600C owners.
From what I've heard, parts have to be ordered from Dell because the parts aren't interchangeable with other machines.
That's interesting what you say about a video card. I don't play games, except a couple of online card games. You still think a video card is necessary? [i thought cards slipped in slots, didn't have fans. BTW]
I'll check the other fan that 7/4 mentioned too. But, I'm pretty sure it's working.
I'm going to replace the power supply, see if that does the trick. Aside from overheating it is a very good machine, IMO.