Also look your Driver config. NVIDIA config has the option to override anisotropic filtering. Make sure it isn't turned off. On the other hand, if your driver config is set to "Best Performance" instead of "Quality" or "Best Quality" you'll end up with those results you're seeing.
Bingo! That's it. On that test pc nvidia cpanel there is an option "anisotropic-mip optimization" which is (By default) turned off. Thanks a lot.
Your PC supports Anisotropic filtering, while the test one doesn't
Another option, you're letting mipmaps to be automatically generated, and it's broken on the test PC's drivers. Update the drivers or use DDS to generate mipmaps manually and easily.
It's going to help a lot if you publish the specs from both machines (including driver versions).
Nice Suggestions My own pc have GeForce 8500 and video card of test pc is GeForce6200 In both pc D3DPTFILTERCAPS are the same and shown in the shot using dx caps viewer Is It Possible That DxCapsViewer show a wrong capacity? ( in Anisotropic filtering)