I don't know what demands serious editing puts on a system but what I'm doing sounds similar to PattyClink's current tasks. My three year old HP laptop* running windows XP does the job with no problems that I'm aware of, using Audacity for most tasks. Typically I start with a recording from a Zoom H2 in wav format which may be as large as 500mb. It can take a couple of minutes to import/export a track but processing is pretty quick.

The only limitation is the poor response of the inbuilt speakers. That's easily overcome with plug-in external speakers or headphones.

*Pentium M 2.13Ghz   2.00 Gb ram
SoundMAX integrated digital audio