An AGP card will fit into a PCI slot with a lump hammer only LOL....
Thats fine what your seeing its using RAM alloted to a PCI card.
Its for DirectX and other programs to "use in PCI mode"
Dont worry about it your not losing any performance and changing it will cause some programs not to run.
Go to
http://www.madonion.com and run 3d benchmark big dload if you have 56k buy a magazine with it on the front cover.
Also go to START/RUN and type Dxdiag and run directx and test your card it will explain it a bit more.
LOL@AGP in PCI slot tho hehehhe
kdja