I have a GeForce 6600 256MB and my Motherboard is : ASUS P4S533 - MX ACPI bios revision 1004 The Motherboard has an AGP slots,so the card is also AGP.
No, just becouse it's AGP 4x and the card is at AGP 8x doesent mean it should not work, most if not every card now that is AGP is 8x, your graphics card should be able to work with AGP 2X, 4X and 8X i belive, infact, even AGP 8x aint used to its full potential in games yet.
Nope, AGP 8x is not compatible with 2x. Only 4x. You'll have a performance hit as the bandwidth will not be up to 8x, but it will still work.
There's different AGP standards: AGP 1.0 = 1x and 2x AGP 2.0 = 2x and 4x AGP 3.0 = 4x and 8x There's voltage differences too: AGP 1.0 = 3.3v AGP 2.0 = 3.3V or 1.5V AGP 3.0 = 1.5V