>For my application, I need some method of not allowing the user to start multiple instances of the executable. If they try to run the same executable, it should simply pop up the currently open executable-- just as many applications already do. I've looked, but can not find an easy way to do this. I'm guessing it includes use of API's of some sort. I would very much appreciate any suggestions on this matter. Thanks.

Check out the Files section of UT. I'm pretty sure there are examples how to do this there.