Since you pressed F12 and were booting from the 7 dvd you may have to repeat the process a few times and wait a little longer for the next screen past the loading files and Windows 7 logo screens to appear. The screen may go black for a few minutes while the 7 installer is in the process of detecting all hardwares before the language selection screen(first seen after logo) appears.
With multiple hard drives here I see that lag at times. If nothing loads after so many minutes you might have to retry a few times before it finally will load however.
Since you are not able to boot in safe mode the other option is the safe mode with command prompt option. Command Prompt at Startup
The live boot off of the 7 dvd however provides the startup repair and command prompt options there making things a bit easier before the final resolve of electing to perform either a repair install or full recovery which you should still be able to avoid. MBR - Restore Windows 7 Master Boot Record