Although most Windows applications place fairly low demands on the display system, putting up fairly static displays and updating them relatively infrequently, interactive games and video displays are very graphics intensive. Game players pay big bucks for fps, or frames per second, which is a measure of how fast the hardware and software can generate new images as the scene changes and objects move. Under about 30fps, the image flickers and motion is noticeably jerky. Beyond 30fps, faster updates aren't noticeable, and the extra processing power can be put to work by reconfiguring the game to generate more complex, detailed images.

The problem is that the software overhead that Windows places between applications and the graphics hardware in order to foster good cooperation, nicely rendered text, and cleanly overlapping windows can slow down a game program or DVD video player and hinder its ability to crank out images. Enter DirectX, a set of application software interfaces (drivers, really) that let applications have much more direct, faster access to underlying display hardware. DirectX also provides hardware-independent image rendering and sound-producing tools that applications and games can rely on; these can take advantage of the hardware adapters' built-in computing abilities, but are guaranteed to workif slowlyeven on inexpensive adapters without hardware acceleration.

Microsoft updates DirectX on a schedule independent of its updates to Windows, and although some software setup CDs come with a version of DirectX, if you play video-intensive games or watch movies on your computer you're better off getting the latest DirectX package directly from Microsoft. To find out what version of DirectX is installed on your computer, click Start, Run, and in the command box, type dxdiag and press Enter. On the System tab, near the bottom of the System Information list, you should see an entry labeled DirectX Version.

DirectX updates are usually not security-related fixes, so they will not be delivered through Automatic Updates, nor will they appear in the "High Priority" section in Windows Update. To check for a DirectX update, click Start, All Programs, Windows Update. Select Custom updates, and view any entries in the "Optional Software" category. Check and install DirectX if it appears.

You can also download and install the latest version of DirectX from www.microsoft.com/directx.