Not booting anymore after changing mobo

[Marscaleb]

I had a hardware fault that I tracked down to being either the motherboard or the CPU, so I decided to just replace both. (And with that I also had to replace the memory.)
My system had been set up with a dual-boot for win 7 and win 10, which IIRC I set up using EasyBCD.
After replacing the hardware, I still managed to boot into win 10 just fine, and after replacing/updating several drivers it appears to working.

However, when I try to boot into win 7 I have problems.
It always prompts me with a "didn't run correctly" screen where it offers to boot into safe mode and all that, but when booting normally it gets to the "starting windows" screen, then it flashes a blue screen and jumps back to my BIOS's logo, and starts the boot process all over again.
I tried booting into safe mode, and (although I wasn't present at the moment it screwed up) it still just went back to the start of the boot process.

I'm not sure where the problem lies, nor how I should go about fixing it.
Is it more likely that my copy of windows 7 got screwed up somehow and it needs to be repaired? Or is this a problem with the dual-boot not working with the new bios, so I need to fix that? Is win 7 having some sort of innate problem with compatibility with this new mobo?

 

[SIW2]

compatibility with this new mobo

maybe. You could try

Make Windows 7 bootable after motherboard swap

 

[Megahertz07]

You didn't give us the hardware specs of the old and new MoBo.

New hardware requires some drivers that are not on the Win 7 files.
You may need to add those drivers (normally USB3.x, SATA and NVMe) to the Win 7 installation. From Win 10 you can use Dism++ to do it.
SIW2 is the one to help you on the task.