If your PC has been noisy since you bought it, there's not much you can do because it's a design problem. Anything you might do to muffle the noise would probably also block the flow of cooling air sucked in by an internal fan, which is the main source of most PC noise.
However, if it has gotten noisier over time, there are a few things you can do, though they will require opening up the case. The innards of computer cases can get amazingly dirty over time as dust sucked in with the cooling air accumulates in the case. This can cause the fan to work harder and more noisily.
The best tool for cleaning is a vacuum cleaner with a hose attachment. Try to avoid banging things too much. If you have installed any add-in boards that you're no longer using, remove them -- they can interfere with cooling.
If your PC is still too noisy, I'm afraid the only cure is a new computer. Desktop PCs have gotten much quieter in the last couple of years -- even as chips have gotten hotter. Some companies have adopted a more efficient Intel (INTC
) case design called BTX, while others have come up with equivalents of their own. Bigger, slower-turning fans, sometimes several of them, move more air with less noise, and thermostats turn fans on only when needed.
Wildstrom is Technology & You columnist for BusinessWeek. You can contact him at email@example.com