>How can I initialize the EXE file so that one cannot open 2 instances at same time in the same workstation or over the network?

* Main.prg
if IsAppRunning("myUniqueApplicationIdentifier")
 messagebox("One instance of this app is already running")
 return
endif
* ...

Function IsAppRunning
	Lparameters tcSemaphoreName
	Local hsem, lpszSemName
	#Define ERROR_ALREADY_EXISTS 183
	Declare Integer GetLastError In win32API
	Declare Integer CreateSemaphore In WIN32API ;
		string @ lpSemaphoreAttributes, ;
		LONG lInitialCount, ;
		LONG lMaximumCount, ;
		string @ lpName
	hsem = CreateSemaphore(0,0,1,tcSemaphoreName)
	Return (hsem # 0 And GetLastError() == ERROR_ALREADY_EXISTS)

Would do it for a single station.
If you want to do it for all users than lock something for that user (ie: set exclusive on).
Cetin