While XP will open files with an EXE extension from the run command without the need to explicitly provide the extension, the same is not true for all other extensions. However, you can control this by adding those extensions to a variable named PATHEXT. This system variable controls which extensions are tried when not supplied. One of our personal favorites is adding the MSC extension, which allows administrative consoles like the Services tool (services.msc) to be quickly opened from the Run command.
Similarly, the PATH variable controls the directories in which XP will search for a file when an extension is not provided. By default, the PATH variable will search three different directories, including C:\WINDOWS, C:\WINDOWS\system32, and C:\WINDOWS\system32\WBEM when a directory is not specified. By adding additional paths to this attribute, you can control which directories will be searched for the filename when a path is not specified. See the steps below for an overview of changing the PATH and PATHEXT variables on an XP system.
Step 1: Click Start, select Control Panel, and then click System. Click the Advanced tab, and the then click the Environment Variables button at the bottom of the screen. This will open the Environment Variables window shown in the background of Step 2.
Step 2: In the System variables section, click Path, and then click Edit. Place a semicolon after an entry (second, for example), and then type the full path to any additional directories you want searched. Click OK. Follow the same steps to add additional file extensions to the PATHEXT variable (for example, .MSC). Reboot once complete.
Step 3: To check whether your new PATH or PATHEXT variables are functioning correctly, attempt to open a file in the new path and with the new extension from the Run command. For example, type services at the Run command, and click OK. In this case, the Service.msc console should open automatically.