My video when i turn on AE pc is laggy

hi, let me start off saying that i have little computer knowledge and if there is a thread that tell me what i need to know please direct me ASAP.

i purchased AE PC yesterday. i turn it on and my video is lagging. a friend of mine told me that i might have to update my driver. i updated it and i set my resolution setting to the lowest. my vid still laggs horribly. i have no idea what the problem is or what i am doing wrong and i have resorted to asking a forum lol

part of me thinks it cause my PC is old and it can’t handle the graphics (my PC is 5 years old and if that’s the case please tell me so.) however my knowlegde is blank and if its a way to get it to stop lagging so much i would like to know so i can get to work on it.

heres some info

microsoft windows XP media center edition 2005 hardrive
AMD Athlon 64 processor
-Intergrated ATI
-ATI Radeon Xpress 200

that’s about as much i know about my PC. any help would be appreciated.