Rupert,
Plug your Mac in and let it charge up. When you get the green light, try to Safe Boot - insert the Intall disk, press the Power button and when you hear the chime press the Shift key. When you see the apple, release the shift key and it should get to Safe Mode. If you get this far a regular boot may be possible. if you can't start in Safe Mode, you'll probably have to re-install OS X.
And the next thing you need to do is buy an external drive and download SuperDuper so you can make a backup after you get things set up again...
Sorry for your loss, but things will work out better the next time - you learned a valuable lesson, the hard way...
Noel