Erasing laptop with no disc, and transferring Spore.?

[samm]

Basically my PC has come under a virus and I need to reformat my hard drive, but I have no disc. Also, I own spore, but you can play that without the disc so I have lost the disc.Basically my 2 questions are: 1. How do I reformat my hard drive without a windows disc (I want to keep my OS)?
2. Is there any way I can move all my spore files, including the game itself, to my pc once reformatted?
Also, I have a 500gb external hard drive so I can store most things.
Thanks, Sam.