My computer won't boot

elito25

Honorable
Feb 6, 2013
7
0
10,510
I have two hard drives. One of them used to be external. I used to use windows 8 but decided to switch to windows 7 so i installed it on my external. A couple of days ago, I accidentally changed my active partion. I reinstalled windows on my internal without using any key as to give me 30 days. When every I try to boot into my old system, it says that the operating system is not found. I was able to go into the new windows. I changed my active partion back but it says the same thing. Whenever I try to boot into my new windows partion, it says that bootmgr is missing. I'm using a gigabyte motherboard and the only other computer at my disposal is a Mac. I don't have a disk drive and have one 4 gb USB. Cant afford another installation of windows and have important files on my old drive. Any suggestions?