forget serial in any new laptop they just dont have them anymore
you will get one VGA out and one RCA out on many laptops just use a spilitter if you need more I dont think a desktop would be any better for this.
Laptop has its own battery desktop doesnt plus a laptop is usually well under 90w if it isnt working hard.
Hibernation doesnt suspend to ram thats standby
Multiple audio as in what way, why do you need multiple in?
you can get cards that do this but they are pretty high end usually and expensive.
with everything that you want even if you went with a VIA board your going to end up with something pretty power hungry with all the cards and stuff, course if your happy with everything showing the same stuff its a lot simpler just use spliters. If your looking for multiple video outputs showing different things I think your in trouble with a 700mhz processor, your going to need a load more than that.
Personally I would say 256 ram isnt going to cut it either as thats the minimum for XP much better with 512 or more