Windows 2000's Application Compatibility utility (apcompat.exe) lets you fool programs into thinking they're running under a version of the Windows OS that's different from the version you installed. Simply set the program to run in a Windows NT 4.0, Windows Me, or Windows 9x compatibility mode. This tool also offers three other compatibility settings: Disable Heap Manager on Windows 2000, Use pre-Windows 2000 Temp path, and Correct disk space detection for 2GB+ drives.

Win2K Service Pack 2 (SP2) includes another way to set a program to run in compatibility mode on Win2K Professional systems. This option is disabled by default. To enable it, log on as Administrator to a Win2K Pro system on which you've installed SP2, then click Start, Run and type

regsvr32 %systemroot%\apppatch\slayerui.dll

When you press Enter, the system presents a DllRegisterServer in C:\WINNT\apppatch\slayerui.dll succeeded message box. You can then modify an application's shortcut to cause the application to run in compatibility mode. To do so, right-click the shortcut and select Properties. The shortcut's Properties window will include a new Compatibility tab on which you can select the Run in compatibility mode check box. This check box enables a drop-down menu from which you can select Windows NT4 SP5 Compatibility Layer or Windows 95 Compatibility Layer.

Running an application in compatibility mode doesn't alter the program; it simply enables the OS to lie if the program asks for the OS version and slightly changes the system configuration so that the program runs in an environment that more closely resembles NT or Win9x. Microsoft cautions that serious problems can result from using compatibility mode to bypass version warnings in installation programs. For more information about this problem, see the Microsoft article "How to Enable Application Compatibility-Mode Technology in Windows 2000 Service Pack 2" (http://support.microsoft.com/support/kb/articles/q279/7/92.asp).