Help, with laptop and new system

Hey i need some help i am workin on building me a new system, i am working with a stock Dell Dimision 8200....its been gutted its just got a psu,cpu and motherboard.....i need mostily advice on ram....Cause i am not Expreniced with RDRAM...

Also i would like some help with my laptop because i know nothing about a laptops hardware,its a old Dell inspiron 2650....i want to upgrade the ram in it..it also has no Upgrades what so ever done to it....its got intel p4 1.6 cpu and 256 mb ram in it

you might just wanna buy a new laptop as upgrading laptops aren't the best idea....

you might want to mention specs on the computer though