thanks all of you for patiently answering my question "About exec() function in PHP: About exec() function in PHP", it has given me an idea of how this works and so. Lots of them pointed the syntax error, my pardon forgot to include the quotes.
Actually I have got a requirement in normal conditions the customer has the .exe file which he needs to normally run from command prompt, where he needs to include the path for the license and config files manually, so that application is valid for installation.
Now he wants a php script where he will enter the web page with his valid login details and with the click of link he should be able to run the .exe file to install the software on his machine. Including the license and config file is my job which I have been working on, on the other hand I am still not clear that this is really possible to run the .exe file on the clients machine when the script runs on the php remote server. What can be the other alternatives to accomplish this. Can anyone clear my doubts?