No, that's good enough. Except for the proccessor I've got a similar system and don't have a problem.
Which service pack do you have for XP.
And try the latest drives for your video card.
Before installing video drivers. remove the old ones in Add and Delete Programs reboot and the install the new drivers. Also try defraging your hard drive.
Note I can't access the ATI driver page right now
http://www.ati.com