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okay, so when WIN10 upgrades, it TRIES to keep all the files, and programs and just work around them.
But to be honest, this is probably the WORST way to change an operating system.
I reccommend a FULL CLEAN install. Meaning all the data would HAVE to be backed up, on a DIFFERENT drive, or whatever.
Then wiping the drive, and doing a CLEAN install.
Because you are getting a HANG-UP on the boot sequence, and can not get into Windows, you will need to RE-install.
Either, you can CLEAN install WIn7, or WIn10.
NO matter which you choose, you MUST have the INSTALL files, and they MUST be on a DVD, or USB drive that you can boot from
This is what i reccommend.
HOwever, you COULD try to repair your windows. and for that you need the INSTALL files for Win10, and again they need to be on a DVD or a USB that you can boot from.
SO, pretty much no matter what you decide.....you MUST get the INSTALL files on a DVD or USB and boot from it.