Disk Boot Failure Instert System Disk and Press Enter

Ok, so i recently upgraded a few components of my pc
Motherboard
CPU
RAM
and a new Case.
once i set it all up, i started the pc, and i got the error message in the title.
So i inserted the windows 7 disc, and then i repaired startup, told me to restart, and that didnt work, i ended up back at that screen. Can someone help me resolve this please, i have tested all the cables, and yes the hdd is being picked up. I inserted an empty hdd and installed a new windows 7 on it, and that works fine, and i can access the hdd that keeps failing.
Answer #1
Your MRB might be corrupted, or the windows installation all together.
You can try re-install or regenerating the HDD.
Answer #2
check your C drive to see if the partition is set to active
paragon partition manager can do that