I run pro-tools 7.0 on a HP Pavilion 5385 with a gig of ram and a 2.6 ghz p4.

The key is I use a firewire connection for my digidesign hardware (digi 002) and run external usb 2.0 hard drives for the audio. (My laptop has 2)I can run 32 tracks of aiff audio at 48K 24 bit with no problems.

If you go to the DUC at the degidesign website, they list many laptops used for digital recording, plus many tips and tricks.