if you run a decent antivirus like trend micro or kaspersky or nod32 then 128 will suffice,not all ram has to be the same size to get the better performance but the ddr will work better than the older sdram. the general rule for xp is: it likes ram alot more than a powerful processor,same goes for 2000 but for 98 it can work very good on low memory compared to xp but a faster cpu is good too,the amd's palamino cpus ran hot but the thouroubred runs cooler,the athlon 64s run alot cooler then the older cpus do(i know cuzz i run a athlon 64 3000+) 64MB for light browsing and some light music 128MB for minor things like browsing and light office work and some music playing 256MB for light gaming and medium office work and music playing 384MB for medium gaming and moderate office work 512MB for medium to somewhat heavy gaming and moderate to somewhat heavy office work 1 Gig For Everything from heavy gaming to heavy office work and soforth. thats just what i've noticed when i work on machines.