First of all see if you have installed Java JDK on your system, if not then head to the below link and get it installed, if yes get it reinstalled.
After this try tiy to open Eclspse, it should open by now.
If you still get the same error message, go and change the path variables.
To do so go to the MyComputer->Properties-> And click on Advanced System Settings
It will open "System Properties" window.