I followed this tutorial and successfully dual boot Win7 and Win8 vhd. But yesterday I got a problem with my Win7 and not able to boot. I use the Win7 installation disk to repair and got back my Win7. But then I lost the Win8 boot option. Since the dual boot is created when installing Win 8 to vhd, I don't know how to recreate it. How can I put back the dual boot without reinstalling Win 8?