Quote: "but you can have dx10 on it"
Windows XP
cannot have DX10 no matter what, it was not coded into the XP code and DX10 and DX11 require specialy coded core elements in the OS for DX10 or DX11 to work.
And X9 doesn't require DX10, If you think that this is the case then download the latest DX9 and if it doesn't work then, buy windows 7 and a DX10 compatible graphics card as that would be the only way and if it works then, I'll take your word for it.
Windows 7, Amd Athlon 7750 Black Editon (64 bit,3ghz + Dual Core), ATI Readon HD 4870 1gb Edition, 4gb Ram.