set the form property windowtype to modal

>I have created a system and compiled it into executables files.In building the executables i chose to recompiled, run after compiling check boxes. And upon the builing it did not generate any errors and the program run correctly and properly.
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>The problem is when i exit the program and tried to run the executables, it start but it doesn't stop in the form where the user must log on (Login form). The program starts and then closes. I have installed the runtime dll to the PC and it doesn't work even.
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>What causes this problem?
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>note: Program must run then show the Log-on form.
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>Thanks