To enable 3D accelaration in your Destop, You should have some supported graphices card. If it is semi supported then it's also O.K... Now you should have some necessary packages , These are compiz, xgl, xgl-hardware-list, gnome-session and libwnck packages. Just install these packages. Next run gnome-xgl-setting from the command line and enable 3D Desktop option. After than just logout and login again. You will get 3D enabled Desktop. Remind one thing it's for GNOME Desktop not for KDE. To enable 3D Desktop in KDE you have to do configuration. Please follow this link
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