I believe you are stuck with your curremt processer unless you are willing to replace your motherboard.(better off trading up )
As for the brand of RAM; look whats in it already,if it has served you well buy that if you can get a good deal.............
IBM T22 laptop,900mhz p3,20g hdd,512mb ram
IBM Netvista M42 40g hdd,1.8g p4,512mb ram
IBM Netvista 933 mhz p3,10g hdd,256 mb ram
Winbook laptop 400mhz p2
Dell 4600 2.8g cpu,120g hdd,256 mb ram(On bottom of list where pc of **** belongs)
768/128 DSL w/LAN(wireless G)