Try

? ShellExecute ( 0, "", "c:\Test.rdp","","",0)
* Or
? ShellExecute ( 0, "Connect", "c:\Test.rdp","","",0)

>Hello, I'm using following code to try to open a RDP-files located on the local c:\-drive.
>
>The function returns 31, which means no associated programm found. I can start the RDP-file by double clicking the file...
>
>I checked the association in Windows and the RDP-extension is linked to the Windows Remote Desktop application.
>
>Used code :
>
>hDCScreen = GetDesktopWindow()
>? ShellExecute ( hDCScreen, "Open", "c:\Test.rdp","","",0)