Thank you for the gif.
.\src\main.c(1099): _main_do_command_line_installs(); Fatal error: Failed to copy Everything.exe: 3
Error 3 is: Path Not Found
This could be the source or destination.
The source file will be: C:\users\user\AppData\Local\Temp\es<random>.tmp\Everything64.exe
The destination file will be: C:\Program Files\Everything 1.5a\Everything64.exe
My guess is the destination folder is missing as shown from your gif.
Everything does try to create this folder before copying the file.
It's very strange that the -install call succeeds.
This means Everything successfully relaunched as admin to process your -install commands.
I suspect Everything is not really relaunching as admin or it is with some strange permissions.
I wonder if something is blocking Everything from running Everything.exe as admin from the temp folder.
Could you please try the following:
Extract the portable version of Everything64.exe to: C:\EverythingSetup
Run the following command as a standard user:
C:\EverythingSetup\Everything64.exe -setup
Please try following the prompts to install Everything.
Does the same issue occur?
The installer does the same thing, extracts the portable version of Everything to your temp folder and runs:
Everything.exe -setup
If the issue persists, please try the following:
Run the following command as a admin user:
C:\EverythingSetup\Everything64.exe -setup
Does the same issue occur?
With the fatal error message shown, does the temporary Everything folder still exist?
The folder location is shown in the install dialog under: "running install script".
The folder location will look something:
C:\users\user\AppData\Local\Temp\es<random>.tmp\
Is something deleting this folder after extraction?
Finally, if the issue persists, please try the following:
Run the following command as a admin user:
C:\EverythingSetup\Everything64.exe -install "C:\Program Files\Everything 1.5a" -debug-log
This will log debug messages to: %TEMP%\Everything Debug Log.txt
It might give a reason why creating the folder C:\Program Files\Everything 1.5a fails..