Description of Video card of my PC is SiS 651_661FX_741_760_760GX_M661FX_M661MX_M741_M760_M7 60GX. How do I know whether it is DirectX9 compatible? How do I know its memory?

Description of Video card of my PC is SiS 651_661FX_741_760_760GX_M661FX_M661MX_M741_M760_M7 60GX. How do I know whether it is DirectX9 compatible? How do I know its memory?

That looks like a catchall description for multiple chipsets from a universal all-in-one driver supporting multiple products. You'll need to determine the actual chipset on the discrete video card or integrated motherboard adapter and then refer to SiS's product information (http://www.sis.com/index.htm) or the card's manufacturer.

The DXDIAG command run from a command prompt may tell you memory amount. Also see How do I determine what type of video card I have? (http://www.computerhope.com/issues/ch000258.htm) for other options.