For those who has an old machine, it is better to keep the windows xp, but if you buy a new hardware pack today, theres no point at still using windows xp lol, and about memory, eveyone might know that windows xp doesnot recognize more than 4gb of ram because of plataform of 32 bits, theres widnwos xp 64 bits that can recognize much more than 4gb. But windows vista and 7, can handle better the cores, making it work faster, since nowdays a quadcore processor is very common.
btw ae putos xD