Does it show 507 error, if it is showing nothing and you end up in a blank screen after plugging in the "Charged" batter then there is some serious hardware issue.

If it is shows 507 error (with a diagonal line (cross) on a cassete) then its fine. If it is then it means that the operating system is successfully deleted. It is same as you format your Computer and your operating system (Windows or whatever) is washed away.
So now just plug in the device and install the Blackberry OS from your PC and follow the instructions in the second link mentioned above.