BOOTMGR cannot be found when using Windows 7 64bit OS install

Little bit of background... please try and bare through my wall of text, I really need some help.

So 4 years ago I built my first pc, it was pretty decent.
about 3 months ago I fried my motherboard, or I didn't idk. either way I threw out my old motherboard and bought a cheap one to get me by.
I installed a shitty 32bit Windows OS on it and it was fine for a while but I often found that when rendering videos from my editing suite it wouldn't be able to render, the program would shut down, or my pc would just crash.

This motherboard was a ASROCk Fatality Z78 Killer with some crappy INTEL i5 something something.


So I asked around and my buddy gave me a new motherboard that had an INTEL i7 960 which I was told would be suitable for a 64 bit OS, which I think I need to render videos properly.

So I removed all the components from my motherboard, unscrewed the motherboard from the case, replaced it with a new motherboard and replaced all the components ensuring everything has power/data cables connected.

Now comes the annoying part, I didn't have a 64 bit OS install disc, so I tried to build a bootable CD from guides online, that didn't work so I tried building a bootable USB to install it, that didn't work so I borrowed my friends 64bit Windows 7 OS install disc to get windows up and running and THAT didn't work.

The message I got was: cannot find BOOTMGR
I've tried starup repair and it says there is 1 root cause to the issue, but as I scroll through the log of the startup repair there is no section with any errors, for all the sections it says error code: 0x0

So start up repair doesn't work, I've tried doing a system restore, and I've tried running the setup.exe file from the command prompt, I've tried messing around with some of the BIOS settings, like boot priority to CD/USB whatever I was booting from.

Not really sure what else I can do. I'm still unsure if it's a hardware issue, or software... considering I just threw in a new mobo to a working machine would have caused some shock.


bottum line... I want a fresh install with access to a windows.old folder so I can access my old files and documents at some point to get to all my footage I've been trying to edit...

I must be missing something... any help would be amazing!!

I'm not really sure how to access like device manager, or find what components I'm using without having an OS.

If there's any information you need I'll try to add it if you ask.

thanks



I'm not really sure how to access like device manager, or find what components I'm using without having an OS.
If there's any information you need I'll try to add it if you ask.
thanks

EDIT: current mobo is ASUS P6T