A great laptop would be an Apple iBook or however they call it.
These laptops are fast as hell. Since you want to start from scratch , that would be something to look into.
Not 100% sure what specs these things have these days but it will be fast enough.
As for Windows based OS laptops ; I have a HP P4 Centrino Dual core , 1Gig of ram , 250Gig Hard disk and I can say it is fast enough for recording as I recorded a few snipets ( only 4 tracks simultaneously ) with a few buddies of mine, including drums , bass , guitars and vocals ,and the laptop had no problems keeping up and had almost no Latency. I do know that I need to use the ASIO driver in my software ( Sonar 6 ) because the other drivers don't work as well. I used a Lexicon Omega recording device (
http://www.musiciansfriend.com/product/Lexicon-Omega-Desktop-Recording-Studio?sku=245505 ) which I sold a few months later.
I would recommend a little bit more ram memory for using plugins because that slows your computer down a lot. And maybe an external hard drive to store some of your music on.
But these days , any laptop will do just fine , as long as it has more than 1Gig of ram.
( 1 is the bare minimum ) . Most laptops have more than 1Gig anyway as Vista requires more juice than XP.