First of all, you can try to find some updated drivers for your existing video card and then install dx9. If you have onboard, see if you can get the latest drivers from HP. You could go out and buy the best 2x compatible card that you can find, and get the best drivers for that. Or, you could completely replace your mobo with a newer one and get your new video card to work. Buying a new computer IS always an option.

There may be a more-universal card with the same graphics chip. The differences between 2x, 4x, and 8x is in the signal voltage.

The card supply voltage is universally 3.3V, no matter what the bus speed..

The signalling voltage is 3.3V on 1x/2x modes, and 1.5V on 4x mode. 8x mode uses a reduced voltage swing of 0.8V.

By definition in the AGP 3.0 specification, 8x cards and boards must always also support 4x.

Here's a couple of ATI reference charts:
ATI AGP Graphics Card Implementation and
BUILT BY ATI Product Reference

I have an Intel graphics card accelerated 3000 in my DellE520 system but I want to use Windows Movie Maker which apparently needs a card with DirectX9 capability. I'm a complete novice. Do I really need to change?