Solved Computer thinks that there are still two operating systems

Here is what I did: Originally I had Windows 7 installed on my C: Drive. I then split the drive into two and installed Windows 8 onto the second half. I then formatted the Windows 7 part, changed it into unallocated space and merged it with the Windows 8 partition. The only problem is that my computer will ask me whether to boot from Windows 8 or 7. If I boot W7 then it goes black and my PC...