ok whats the basic difference between these two?? right now i have a SONNY VAIO: XP P4 2.53GHz 512MB 120GB DVD-RW..... but i can return it and instead get a (cheaper, money wise)EMACHINES: Athalon XP 26000+ 2.13GHz 512 MB 120GB DVD-RW/+RW. The Athalon cost around $175.00 cheaper. ..SO basically I'm asking which one should I stay with and why? Also what's the diff. between Athalon and Pentium....Also i was noticing that my computer says that I have 504MB when I thought that i had 512MB. Is it cuz I've already saved stuff? Also the Athalon says that it has 512MB but i noticed that it says it has 480MB, is it cuz somebody saved some stuff in it(it was the display model). Thanks.