Really! Hmmmmm... I'll have to save up the money though, is there anything I can do in the mean time?
You could try this site to see what your pc can play.http://www.systemrequirementslab.com/cyri/
It will point out your pc's weaknesses.
Honestly i wouldn't spend any money on a 10yr old pc as far as trying to upgrade main components.
I am building a client a pc for under $600 including WIN7 HP 64bit at the moment that will run Assassins Creed.
Might not be on high settings but playable nonetheless..