There's no substitute for good hardware and it's even worse when you downgrade!

Yea....but strange....are you sure you aren't still using the Windows graphic drivers?

Any card is an upgrade from those...and any card today are more advance then what you tell.

When you removed those graphic drivers and restarted the PC...did it see your card?  if not...did you go to controll panel add/remove hardware and let it search for it....if it don't find the card...you get the option to pick from a list.

The main question is..Have the PC told you that it has discovered a new item (card) ?

Go to controllpanel...screen...and look in the last option....ther you will see what drivers your pc use today.
Good luck

If this doesn't work, replace the motherboard driver.  Have seen that many times contribute to graphic performance.  Standard Windows MB driver support for AGP is only at 1X speed.  More robust cards are 4X or 8X or whatever and you need the hardware specific motherboard driver in place or even the correct driver from the graphic card will not help.  Also, make sure you are running DirectX 9.0c.  Between me and Rhuto, we'll get you lots of ideas.

My computer is crap. It won't even support the graphics cards it's supposed to. I checked to see if it was the card, but it worked fine on my sister's computer. (She yelled at me for messing with her computer, even though it's a much better card, and then yelled at me again for replacing her old one after she asked me to. She just loves to bitch at me.)

Did you get your sister's permission?  If not, you deserved what you got.  (I have a teenage son and daughter and my son always thinks he does not have to ask his sister anything.  Bad habit, he has).