Windows 8 and windows 7 dual boot not working

I dual booted windows 7 and windows 8 and I started it up and played with windows 8. Then I wanted to go back to windows 7 so I shut it down and clicked on windows 7 OS then the screen went black it started updateing and now it wont let me go back to windows 7. It also says SFcon.dll is not working.

I am quite sure that while doing the installation, you have messed up with the boot settings and that this is the reason that Windows 7 become unbootable. You can make use of some VMware to get this resolved.

Would you mind explaining to me what VMware is?