I personally prefer approach showed in API #12710 by Ed Rauh. It's very simple and reliable.

>I'm using a code that is similar to this program. I think it was based on article written by George Tasker.
>
>>Hello Kevin
>>
>>I tried the "FirstInstance.prg" and it worked on my pc (had vfp installed) but not on any pc's without vfp full version install
>>
>>of course they had vfp runtime vfp6r.dll ect ....
>>
>>do me a favor and tell me if you get it to work.
>>Thanks
>>
>>>Hi
>>>
>>>I need an app to only be run once at one time.
>>>
>>>What's the best way to detect if a VFP app is already running ?
>>>
>>>Thanks
>>>Kev