>Need to know if there is a good way to detect if an application is already running.
>
>I have an application that requires that only one instance be running.
>
>If someone tries to run the application again, force the one that is already running become the top application.

By referencing it with the title, you can use that approach:

IF CheckWin('My title')
   MESSAGEBOX('You can only have one instance of this application in memory.',48,'Title here')
   CANCEL
ENDIF

FUNCTION CheckWin
* Routine which sees if an application is active by looking for its
* Window title
* expC1 Window title
PARAMETER tcTitle
DECLARE INTEGER FindWindow in Win32API as FindWindow STRING, STRING
RETURN IIF(FindWindow(0,tcTitle)>0,.T.,.F.)