I believe you will need to keep tapping DEL
as soon as you run the Windows 7 VM to go to the VM BIOS, then set the CD/DVD (ISO file) to be first in the boot priority then the HDD. This way you will see the usual "Press any key to boot from CD/DVD" at boot to boot from the ISO like a DVD to go to the System Recovery Options
(like in option two at link).
Hope this helps,