Is it possible to dual boot Windows 8.1 and 7 on the Dell Venue 8 Pro?

Have a new Dell Venue-8 Pro with win-8.1 pre-installed. Added a memory card as partition-D. Now want to install my copy of Windows-7 to that partition, either stand alone or as dual boot, but cannot get the tablet to boot from a USB DVD drive. Am able to get into the BIOS but no boot sequence offered, just "Windows Boot Manager" which won't access the DVD. All other boot options in the Bios are greyed-out inaccessible. even w/ disable/enable EUFI Secure Boot.

Desperation; I can see files on the DVD from within W8 so ....Try to install W7 from within W8 & get error message that W7 cannot install on a device currently powered by battery (it's not! the tablet is plugged in through a 4-port USB hub with 2.8 amp wall power-pack).

Any help, suggestions or procedures seriously appreciated. THANKS

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