I am using an oldish Compaq Presario desktop PC for audio editing and it probably has a lower spec than more recent laptops.

It has an AMD Athlon processor (I'm not sure of the clock speed, but I suspect around 1.25MHz), with 384MB RAM and since February has been dual boot WinXP/Ubuntu Linux. The Ubuntu is a bog standard installation.

I am not after professional standards and I record on an Edirol R09 and use Audacity for editing with no problems. Audio editing is fine and does not feel slow.

If you use a separate recording device, then you can record in another room (which is what I do) so fan noise is not then an issue.

I have recently bought a video camera and use Kino (similar in capability to Windows Movie Maker) for simple edits and that is fine too. Exporting the final video takes a little time, but is not unduly slow.

Overall, unless you are a pro, an older machine is perfectly capable for basic audio and video editing.