Changed Motherboard-Win 7 can't recognize it?

Hi, I run win 7 8gb ram gtx750 vid card and an athlon whatever processor, it recently died ( no boot, no spin on cpu fan) so I replaced the PS and the MB, went from Gigabyte to an MSI gaming type board, both AM3+ slots. The MB seems fine, but windows won't start. I removed all the sata but my SSD that I boot from, win tried repairing a couple times, no go. I logged in as admin and looked at the diagnostic, shows a sys config error, the other tests all passed. So, do I have to find my win 7 disk and reinstall it? If I use the image file, will it be like a fresh install or think I am in my old machine? First time I ever swapped motherboards, I did go through similar crap when I got the SSD though. Is there a way to fix it in DOS? Thanks in advance.