you might need to get into bios and change the boot order to usb cdrom, usb hdd ahead of normal boot in c drive which is windows boot .
to get into bios, hold both windows button and power key for 4 sec.
or if the tab is on, do charm bar, setting, change pc setting, general, under advance startup click restart now, troubleshoot, advance options, uefi firmware settings, restart. it will take you to bios.
if it still does not boot, you might look to play with boot legacy and uefi boot and/or secure boot, which you need to set up supervisor pass code