Look man, I bought a Nusystems laptop - a desktop replacement - 3 ghz P4.

Do I wish I had bought a Centrino instead??? Possibly.

If you buy a P4 laptop with a 3ghz cpu (or faster), you can forget good battery life. They are power hungry as hell. I have a dula boot set-up, ie I have one boot partition which is lean and trimmed of all the stuff that can slow your system down - ie it's built solely for doing audio - and I manage about 30 mins battery time from from this partition. Obviously as part of this set, I don;t have any battery saving services running etc, but it is still a shockingly low amount of battery time.

With a Centrino, I would expect maybe 4 or 6 times as much time...
This is because centrinos run at a significantly lower voltage.
Another thing to consider is that the centrinos run cooler, and as a result should use their inbuilt fans less, adn resultantly should be quieter than P4s. However these advantages come at a price, plus there is a rather skecthy upgrade path for centrinos as well, depending on what inital machine you buy. This time last year when I bought my laptop I would have needed to pay almost 200 quid more for a centrino system of comparable performance to the P4.

So a few things to consider - for me - I didn't have enough cash to buy the centrino system, though if I'd had the extra cash, I would have...

As for your ram quandry? What the hell are you going to be running???
Check the ideal system specs for the software you are running, and use the ideal requirements. 4 gig of ram is mental, and may actually hamper some software's performance.

My laptop kicked off life with only 512meg in it, and it functioned admirably. I then bought an additional 512 to take it up to the 1 gig mark (it's full complement) as I thought it might help me use more instances of plug ins - however this proved not to be the case. Ram is important if you want to run any sample based instruments, like Spectrasonics Atmosphere, or Trilogy, but what is equally important in this instance is how fast the hard drive is - don;t settle for anything less than 7200rpm unless it's stats stack up...

Hope I've given you some good advice...

BombJack