Computer Won't boot after replacing HDD [SOLVED]

Galaxy4you

Commendable
Feb 5, 2017
23
0
1,520
I recently changed the secondary HDD to a new one. I have an SSD as my main drive. After replacing the HDD, I turned my computer an error popped up "BOOTMGR is missing Press Ctrl+Alt+Del to restart". I have many important files on this computer. I have tried putting the old HDD back but it did not do anything. Is there anyway to fix this or do I have to reinstall windows (which I don't really want to do because of the files). I also Don't have my windows 7 dvd.

system specs;
Intel pentium G3220
PNY gtx660
Drevo X1 120GB SSD
WD 500GB HDD
Mobo: ECS essentials H81H3-M4
OS: Windows 7