Windows XP Professional allows you to run programs using user credentials that are different from the currently logged-on user. Using different credentials is useful if you are troubleshooting a user’s computer and do not want to log off and log back on using administrative permissions just to perform a troubleshooting task or run a particular program. Using this method is also more secure than logging on to a user’s computer with administrative credentials. Running a program with different credentials in Windows XP Professional relies on a built-in service named the Secondary Logon service. This service must be running (and it is by default on computers running Windows XP) to run a program with alternate credentials.

To determine whether the Secondary Logon service is running (and enable the service if it is not running), follow these steps:

1. Log on to the computer as Administrator or as a user with administrative permissions.

2. From the Start menu, click Control Panel.

3. In the Control Panel window, click Performance and Maintenance.

4. In the Performance and Maintenance window, click Administrative Tools.

5. In the Administrative Tools window, double-click Services.

6. In the Services window, locate the Secondary Logon service on the list of Services.

7. If the status for the Secondary Logon service is listed as Started, the service is enabled, and you can close the Services window. If the status is listed as Manual or Disabled, right-click the Secondary Logon service and click Properties.

8. On the General tab of the Secondary Logon Properties dialog box, on the Startup type drop-down list, click Automatic.

9. In the Service Status section, click Start.

10. Click OK to close the Secondary Logon Properties dialog box, and then close the Services window.

If the Secondary Logon service is running, you can run a program using different user credentials than the currently logged-on user. On the Start menu, right-click the shortcut for the program you want to run. On the shortcut menu, click Run As. In the Run As dialog box that opens, you can run the program as the current user, or you can enter an alternative user name and password. Microsoft recommends logging on with a limited user account and using this technique to run applications that require administrative privileges.