ok, so I found a lot of information on how to make a USB flash drive bootable. But none of them worked on making an external USB mechanical hard drive bootable. I finally found a procedure which actually worked! It is posted here by Kevin.
Note 1: On step #2 where he talks about running the bootsect command….there is something more which needs to be done. The CMD prompt on my win 7 machine had to be elevated (right click on the cmd and choose “run as admin”). After that this command made my external drive bootable:
bootsect /nt60 G:
Yahoo! (thanks Kevin!)
The tool from Microsoft does not work for external Mechanical HDDs. It only works on USB flash drives.
More useful links: