If you are only paying $25 go for it. AGP is backward compliant but that 8x card will only have half the bandwidth. the older AGP cards will not work in newer systems because of the voltage differences and the new AGP pro slots are configured (3 openings at the AGP interface on the newer cards vs 2 on the older cards) differently and the older cards will not fit into 4x/8x AGP slots.
Noli Nothis Permittere Te Terere!!
EVGA 680i, Dual EVGA 8800GT'S (650/950), 4 gigs OCZ DDR2 1066, Intel Q9450 at 3.8 Ghz, Koolance Water Cooled, Dual Plextor16x DL DVD+/-RW. Dual WD 250gb 16mb Cache Sata 3.0. 3DMark06 score = 19,168.