USB drive won't boot into windows but reboots

[cmf21]

Cloned my fathers harddrive so he can still boot off something and have his files til we reformat his other drive. Computer starts booting off the usb drive but ends up rebooting. Any suggestions???

 

[BlueAcolyte]

Windows can't boot off external hard drives without some modifications.

 

[cmf21]

What do I need to do to get it to do so?