Retail disc should work...
Try your COA there: http://www.microsoft.com/en-us/software-recovery

If not, probably through torrent because I don't really trust other direct download sites
http://mirror.corenoc.de/digitalrivercontent.net/

EDIT: well, you can direct downloading, just make sure you check the iso's hashes against the hashes listed on the above site so to give you a piece of mind

This post has been edited by TruboXL: Jun 27 2016, 09:27 PM

at this point i think you better opt for sending to manufacturer to help you revert to win7

not saying that the iso will not work, it will accept your key during install but i won't guarantee it will allow to activate after install...
it needs some sort of custom recovery iso which only oems have...

sorry can't help you anymore

also is your coa specifically for windows 7 or other os?
that oem saying not support because its because i think is that the option for oem to use custom recovery iso is only for that os and not in a technical way

edit: i have no idea what i am saying please do try... this used to be the method when dealing with coa and now m$ft want to confuse everyone that coa only can be used by oem to reinstall... Source1 Source 2

so much edits are done

This post has been edited by TruboXL: Jun 28 2016, 02:00 PM

If your laptop originally preinstalled with Windows 7 of course you can clean install back with the DVD...

Probably you need to enable some legacy features like CSM in UEFI to install Windows 7 properly and look out for USB3 drivers if you have USB3 ports (or just disable USB3/xHCI support in UEFI and enable legacy USB support)...

I thought Windows 7 already has some EFI files that can be boot from UEFI?

This post has been edited by TruboXL: Jul 2 2016, 04:05 PM

Looking up the tech specs if I am not mistaken, there's hardly any new bits that Windows 7 lack, maybe only that USB3 drivers... but you are using DVD... and the images of your UEFI I came across the Internet doesn't seem to include disable xHCI option

I look up but definitely cross out the possibility that your DVD is corrupted...

There's also a possibility that you are missing chipset drivers, I dunno but if you installing into SSD then maybe you really need to find that Rapid Storage Driver...

I have to stop, I probably will mislead you further 'cause I don't really know