your pc specs can be found here :
http://www.acersupport.com/desktop/h...00g_specs.html
as Monty said its not worth it to upgrade or get a new vidcard for your desktop pc because its old and your money will be wasted.
you can build up a new budget system for less than 350 dollars.(i can help you with that)
or if you really want to get a new video card you should look into AGP cards(wich are now extinct) but there are still a few sold on the market.
Heres a list of AGP cards on amazon.com (i recommend the ATI 3850)
http://www.amazon.com/s/ref=nb_ss_gw...ds=AGP&x=0&y=0
a video card upgrade wont be enough as Spore will need more ram than 512mb, you should upgrade to 2gb ram.