Windows 10: Dual Boot Win 10 to Win 10

I have problem related to setting up a dual boot. i am running Windows version 20H2 .
When I tried to install windows on a partition using the latest Windows 10 USB installation, the setup continually rebooted after copying the installation files. I tried several times and thought my USB might be bad, so I made another Win 10 installation/with updates on another USB drive. Again I got to a point where the files were copied and the computer just rebooted and started over again.
At that point, I pulled the USB and tried to boot to my C: drive where I had windows 10 installed, but was unable to as the boot offering was several drives such as Windows 10 - 3, 4, 5, etc, none of which worked.
Luckily I had made a boot CD that I created with Macrium and when I booted from it I was allowed to copy BCD files to my C drive and was able to boot to my original Windows 10 (the one with no sound).
Today, I decided to format the partition and wipe off the files on it.. Again I couldn't load Windows 10 using the USB as it kept stating that an error had occurred and windows couldn't continue, press any key to reboot, at which point it came back with the same error.
So, I tried to boot to C drive again and got the following error.
"Recovery - Your PC needs to be repaired: The application or operating system couldn't be loaded because a required file is missing or contains errors. File \Windows\System32\winload.efi
This time I couldn't boot from the Macrium CD or the USB, and was able to only when I switched the boot to "legacy mode". Once I boot up again, I repaired the boot files with Macrium and was able to boot back to my original Windows 10.
I set up a dual boot years ago, without a problem, so I can't see what I'm doing wrong. The initial USB drive I used must be good because I successfully reinstalling Windows 10 on my C: drive and fixed a "no sound" problem.
Can you guys help me? Thanks

:)

 

Win 10 boots...

I can't answer to the speed of Win-8 booting. I tried the Win-8 preview and went back to Win-7 after a month. They say that Win-8.1 is a lot better than Win-8 was.
My Win-10 TP is working well ATM.

 

Win 10 boots...

Interesting that it works on that oldie but goody laptop.

I don't notice any speed lags with Win-10 TP, but I'm using it on an i5-4670K system with an SSD for the boot drive, so it's snappy.

 

Win 10 boots...

People have Win 10 installed?