>What's "best" is strictly a matter of opinion. I prefer using my Is_Run32 function (which is available in the download section under Win32 and other APIs). Some others might suggest trying to use DDE, but that's totally unreliable in my opinion, since the application must support it.

I disagree. If the application supports it, then it's VERY reliable. Basically, it's difficult to find something safer than this method.

If the second app is yours and you can change its code, then there's nothing to be worried about with DDE.

Vlad