If you can boot in safe mode, I would try running CCleaner. It seems there's something wrong with Windows itself, maybe not even directly linked to the driver. If it's an old installation of Windows 7, it also might be time for a clean install (and yes, I hate saying that!). Sometime, it's just easier to start over with a new OS installation than trying to find some old/unusual bug incrusted in an old installation...
sounds like a modified gpu-bios for me
run Windows SafeMode!
if you have video there you can download and run: atikmdag-patcher.exe and it will work than in normal windows
you get into safemode if you interrupt boot 2-3x with a poweroff
Here is the latest AMD Driver for Windows 7 x64 for your R9-270X: AMD Radeon™ R9 270X Drivers & Support | AMD and the Release Notes: Radeon™ Software Adrenalin 2019 Edition 19.4.1 Release Notes | AMD
What is the Make & Model of your Motherboard and do you have the latest BIOS version and CHIP Set installed?
Does your R9-270X does the same thing on a different compatible computer?
When installing the AMD Driver, what Error message pops up or any error messages when it starts to boot into Windows with no video?
Are there any Motherboard TROUBLE L.E.D.s or TROUBLE DIGITAL CODES or more than one BEEP when booting up with a black screen?
NOTE: Try downloading the latest Windows 10 version using the Windows Creator's tool and install it on a USB Flash drive or burn it to a DVD Disc. Then input your Windows 7 Serial Number during the beginning of the Windows 10 installation. That way your Windows 10 is free and gets activated at the same time.
If the Windows 7 Serial Number doesn't work, then after installing Windows 10, go to Windows Settings Activation and click on "Change Product Key" and input your Windows 7 Key. It should then automatically activate your Windows 10 permanently as long as the Windows 7 Key is legitimate and not illegal.
if you get no video in win but at boot than driver doesnt like the bios of your card
Okay I know you have had a lot of other good advice here. I have an R9 380x that was having these same problems and still would be but I found out how to get it to stop, if the card is not dammaged from this happening.
Not trying to scare you but there have be a ton of threads on this issue.
To get the driver to load you have to ( and I know you have done many of these things but you have to do them all) do the things I am going to list.
Disable Fast Startup/Hibernation
Disable Windows Update from Updating Drivers. Win Aero Tweaker from winaero_com can make this registry change for you on Windows Home or Pro easily, it's a free app.
Make Sure Windows is fully Up-To-Date
Have current driver downloaded and ready to load locally.
Run DDU from from Safe Mode with Internet Disabled
Leave Internet Disabled Reboot
Install Driver, Choose Clean Install, if not available that's good DDU did it's full job! Internet Disabled, this is a must!
Restart and Pray for the best.
If it is still not starting your card may already be fried at this point. This black hang issue in my opinion for many killed their cards. Many kept trying over and over to get Windows to go each time damaging the cards. I was lucky and noticed that not only was it black screening but realized the chip was overheating and shut my machine off. Then eventually figured out why it wasn't loading in the first place was Windows Update was corrupting the install.
I hope your card is okay and this helps.
Thus far everyone of these I have seen reported to AMD they don't acknowledge an issue they blame the hardware. To me it is obvious it is an issue with the installer. This seemed to affect a ton of R7 and R9 owners but AMD has never acknowledged why the driver install only corrupts on these cards. I do know however whatever it is Windows update is also stepping in and messing it up.
That would explain some threads here at AMD Forums in the past where R9 and some R7 would stop working after the computer crashed due to video or after a Driver update and the computer restarted with no signal and a defective GPU card.
In some of the threads I did mention to the Users that there were other Users where their R9 or R7 failed to work after the computer crashed or the AMD Driver was updated.