which tells me you have an AGP 4X graphics card slot.
here's your options.
These cards:
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=2010380048+1069609639&QksAutoSuggestion=&ShowDeactivatedMark=False&Configurator=&Subcategory=48&description=&Ntk=&CFG=&SpeTabStoreType=&srchInDesc=