(i don't have the win7 disc or any serial key because the disc doesn't comes with my laptop)
Your Win7 serial key should be on that Windows 7 Logo sticker on your laptop.
First of all I'd suggest you make yourself a Windows 7 Recovery Disk/Boot Disk
before you try anything else.
Then you could make a System Image of your laptop. It's on the same backup menu you saw making your Recovery Disk.
Also check with Asus and see if you can order a Win7 DVD from them.