Just for future reference for everybody else:
The x2, x4 and x8 associated with cards and motherboards refers to the bandwidth of the interface, and in essence, the higher the better. In general, you can run an AGPx8 card in an AGPx4 slot, for example, though you will lose out on performance.
However, there have also been changes to the specification of the AGP slot with each iteration, including voltage. This means that an AGPx8 card *should* work in a x4 or x8 slot, though probably not a x2 slot due to the difference in specification.
If your motherboard is running an AGPx2 interface, it is seldom worth putting a relatively new card in and you may be better off saving for a new motherboard, CPU and RAM.