The Intel HD Graphics 4600 (iGPU) in my i7-4770K system is running a driver provided by Intel, Date 29/09/2016, Version 20.19.15.4531. OS is Windows 10 Pro.
When installing Windows 10 on old hardware, I always boot offline, because I want to use a Local Account. None of my PCs are using a Microsoft Windows Account.
When Windows is installed I connect to the internet and soon after, the screen goes black for a few seconds and the Desktop reappears in higher resolution mode, when the video driver automatically updates from Basic Adapter.
I check Windows Updates, allow the PC to download and restart. Then I check Windows Updates again and it continues updating. Rinse and repeat.
Next I check Device Manager and look for hardware with yellow exclamation marks, indicating a lack of drivers.
These days, especially on old Xeon server boards, I find it easier to download the optional driver updates offered by Windows Update, instead of trawling the web looking for obscure drivers that might or might not work.
On modern boards I decide whether or not to run the mobo driver updates, depending on how the system is behaving. If Windows Update can't find a driver, that's when I run the mobo manufacturer's driver package. If a 10GbE network card drops frames, I update the driver. Otherwise, I leave well alone. Some driver updates cause more trouble than they're worth if they contain bugs.
not sure if I am in Administrator account or user accout.
Open 'User Accounts'. The name of the account you are currently using should be displayed.
On my machine it shows "Local Account. Administrator. Password protected"
This means the account I'm currently using is Administrator level. You can ignore the Local Account Password protected part for my account. Your details may differ.
Another thing to check in the BIOS is GPU priority. Sometimes it's set to Auto, other times to iGPU or PCIe (the actual names may differ). Get it wrong and the screen could go black when the BIOS switches the output to a port with no monitor attached.
I had one system which displayed black screen during POST on a plasma TV connected via HDMI, but the same TV worked fine and displayed the BIOS screen when I used the 15-way VGA input.
I assume both your monitors were connected to the R9 270X GPU?
People have been having trouble with Windows 10 and R9 270 cards.
https://community.amd.com/t5/pc-dri...rs-for-radeon-r9-270-on-win-10-64/td-p/489791
https://www.reddit.com/r/AMDHelp/comments/vw3cte/unable_to_install_drivers_for_r9_270/
https://www.amd.com/en/support/down...5/radeon-r9-200-series/amd-radeon-r9-270.html
https://umatechnology.org/windows-10-graphics-card-compatibility-list/
"Many Radeon HD and R9 cards are compatible with Windows 10, particularly if the latest drivers are installed. Users may experience performance limitations in modern applications, given the age of these cards."
I stick to GT 710, 720, 730 or more recent cards for Window 10. If a GPU is too old to fully support Windows 10, I leave it running as a Microsoft Basic Adapter in 1024x768.
Your R9 270 might be too antiquated.