Windows 7 gets started automatically even after installing elementary OS. In short I am not getting an option which OS I want to run/select.... windows 7 gets started automatically and I am non technical man.... I feel that linux is still not for common man, but only for technical person?
That shouldn't have happened; I am not sure that all went ok with your installation.
(Installing and using Linux these days and especially ubuntu-based ones is easier than ever and easier than using Windows or Mac I think, but there are some settings during installation that you may have touched and changed in the wrong direction.)
If you are sure elementaryOS was installed:
Boot from live usb
Install Boot Repair
Try: Recommended repair
Please report back.