When ever I use a program like Diablo or Half-Life it will go back to the desktop every now and then

From a Microsoft web page: If an older application gives you trouble when running Windows XP, you can set the compatibility properties manually so that the program runs in a different mode, such as Windows 95, or in a different display or resolution setting. To set the compatibility properties for a program: 1. Right-click the executable or the program shortcut to the executable, and then click Properties. 2. Select the Run this program in compatibility mode check box. 3. From the list, select an operating system that the program runs in comfortably. 4. If necessary, also change the display settings and/or resolution, or disable the Windows XP visual themes. Run the program again when you?re finished changing the settings. Adjust the compatibility settings again if the program is still not running smoothly: a program that's unhappy on Windows 2000 may flourish on Windows 98.