"PC MINIMUM Windows(R) XP DirectX 9.0c (included) Pentium 4 1.4GHz 256 MB RAM 400MB GB free hard drive space 2x DVD-ROM Drive 128 MB Shader model 1.1 compatible video card* Windows compatible sound card* Keyboard, Mouse
PC RECOMMENDED Windows(R) XP DirectX 9.0c (included) Pentium 4 1.4GHz or better 512 MB RAM or above 400 MB free hard drive space 2x DVD-ROM Drive or better 128 MB Shader model 1.1 compatible video card or better* Windows compatible sound card* Keyboard, Mouse
*indicates that device must be compatible with DirectX 9.0c."
You will see that your 661fx is an onboard graphics chip that has only SOFTWARE support for DirectX 9.0
The Game demo needs full HARDWARE support for DirectX 9.0,which is why you are getting the DirectX error.Your graphics card does not support the game.
You also need 128MB of Video ram and I think yours can only use 64MB.
Even if it could technically support the Demo it would not play it at anything like a decent frame rate.The SiS661fx is one of the lowest performing onboard graphics chips available.....errr sorry to break it to you like that :(((
Quite simply you need a much better dedicated graphics card to have any chance of playing this Demo.