video card installation

I bought a Radeon 256MB Hypermemory Video Card. Unfortunately, when I went to install it…it didn’t fit into my desinated PCI slot on my motherboard. Before buying it, I made sure to read the specs..ie Pentium 4 processor…Is there an adapter I can purchase…so I can use it..If not I’m screwed, since I bought it from Comp USA..ie they’re going out of business and won’t accept returns.

Thanks

MIKE