I have faced the same issue. To solve the problem, follow the following steps:
Window (Eclipse Menu) -> Show View -> Error Log
if Error Log is not there, then:
Window (Menu) -> Show View -> Other -> General -> Error Log
Once the Error log is shown, Go to Help (Eclipse Menu) -> Install New Software
Check the Error log, most probable you will see an exception there.
Check the exception, most probable it's caused by java.lang.IllegalStateException
Check the path mentioned in the exception, if you see ".Lock" in the path, close the eclipse then go to the path in windows machine and delete that folder.
now go to the eclipse "exe" file that you're using and open it as an administrator, then try, most probably this will solve the issue.