On systems with very old or inadequate graphics sub-systems the greyed-out 'AGP texture acceleration' setting will simply relate to the display circuitry not providing the features required for certain video games. Please do not send us further queries unless your PC's graphics accelerator is actually suitable for the games you are trying to run.
Since this question was originally posted in October, 2005 we have had numerous further questions lodged by people trying to run very recent games on systems which have integrated Intel graphics, for example. MOST INTEGRATED INTEL GRAPHICS SOLUTIONS ARE UNSUITABLE FOR MODERN PC GAMES!
The AGP texture acceleration setting will be greyed out on systems which do not provide the capability, and in this circumstance there is no 'tweak' which can correct the problem. A suitable add-in display card is the only option available for people suffering this particular problem, and if there is no provision for an add-in graphics card then the system itself would not be suitable.
Generally, when AGP texture acceleration is unavailable it will be either because the motherboard chipset drivers haven’t been loaded or because drivers were loaded in wrong order. I’d suggest you try the following:
• Uninstall the display card from Device manager. Uninstall any related driver entry you might see in Add/Remove programs. Reboot and cancel out of the hardware detection dialogue.
• Install the most recent motherboard chipset drivers available for your motherboard. Reboot.
• Install the most recent driver available for your graphics card from the 3DLabs website.
• Update DirectX to the latest version. (Or reinstall DirectX)
That should hopefully do the trick. AGP texture acceleration unavailability usually results because the AGP miniport driver (part of the chipset driver set) hasn’t been installed correctly.