Verified answer

yes your computer has a PCI-E slot, But before you upgrade your video card BUT you should really think about the 9500GT, it is the successor for the 8500GT, it is cheaper, and much better.

http://www.youtube.com/watch?v=WJPkJyDmH10

ps: UPGRADE YOUR RAM!!!

Emachines w3503 has 300 Watt Powerman FSP300-60GT power supply and a PCI Express (PCIe x16) slot available.

8500GT 512MB models requires

Minimum of a 350 Watt power supply.

(minimum +12 Volt current rating of 18 amps)

There's should be a spec card on the bottom of your machine. Also, if you pull off the side of your box, the PCI-E card is clearly labeled such.

This'll tell you too, it's an amazing freeware tool:

PC_WIZARD, www.CPUID.com

Select the mainboard icon on the left then click on mainboard again on the right, the info on it will display below.