Enter BIOS setup and confirm your onboard GPU chip is enabled, unplug the card.
Reboot into Windows 7. What error is given?
Reboot into System Recovery Options
to run Startup Repair repeatedly, report back findings.
Try entering the Device Manager using the method at the end of this tutorial, see what driver is given the Display adapter and what state it is currently in. If a driver is present, uninstall it to see if install will complete. Device Manager - Access During Windows 7 Installation
After trying these steps with onboard, if necessary try them again with the video card as your chip may be failing.