Hi
I depends on what you mean by a boot disk
This Google search gives some useful info
https://www.google.co.uk/#q=windows+7+emergency+repair+disk
It assumes you have a working windows 7 PC
The windows 7 DVD can perform similar emergency work
A win 7 with integrated service pack 1 ISO downloaded from digital river will also be usefull
Microsoft have a utility to put a win DVD or ISO onto a bootable usb memory stick
Regards
Mike Barnes