Possible to boot/run from external USB HDD w/ Vostro 3560?

Greetings!

Just acquired Vostro 3560 BTX.  Disabled mSATA (please don't ask why), reformatted internal HDD into OS and user partitions, and normally boot from internal HDD. The machine works great, and am very satisfied...  but also want to boot/run occasionally from external HDD on USB.  Have configured \Boot\BCD correctly on external HDD partitions and can load boot manager from external HDD, but selecting external Win7 partition immediately blue-screens.  Before that can be analyzed, we're right back in boot loader error screen.  This same external Win7 partition can be loaded and run successfully on Dell XPS 8300 via eSATA (external HDD in Apricon enclosure with USB2/eSATA connections).

So... Is it supposedly possible to boot/run from external USB HDD w/ Vostro 3560?

Or... would it be better to install ExpressCard/34 eSATA controller (Addonics, Syba, Sonnet Tempo)?

Thanks!