I think I know what's your issue here...
WIth the flashing of the Ozmosis flavored BIOS the IGPU/IGFX is activated and set as "Initial Display Output".
In that case you have only two options:
1.
use ESC-key while starting the box until the complete screen turns red, than use the DEL-key to get into your BIOS.
2.
If that doesn't work, remove the GT 640 and connect your monitor to the onboard graphics outlet, then use the DEL-key to get into your BIOS.
If you've reached the BIOS, use the following settings:
Initial Display Output : IGFX or the Slot which should contain the GT 640, which should be "PCIe 1 Slot"
If you also want the internal Graphics (HD4600) to work, you should set:
Intel Processor Graphics : Enabled
Intel Processor Graphics Memory: 32M
DVMT Total Memory Size : MAX