Installation problem: "DeleteFile failed; code 5"

In trying to upgrade to version 6.5.1, I keep getting an error. I've tried installing immediately after rebooting, but it still occurs. I've attached a screenshot of the error message. Any suggestions?
Thanks!

Please run the installer with /log=C:\some\path\installer.log commandline parameter and post the log here.
https://winscp.net/eng/docs/installation#automating

Sorry, I don't know how to do what you're asking. The only way I know of to run the installer is to double-click on the "WinSCP-6.5.1-Setup.exe" file. I'd be grateful for step-by-step instructions to do what you're suggesting.

Ok, so please try restarting your computer and running the installer as the very first thing afterwards.

Thanks – tried that, same result.

Ok, so the last option is to uninstall (keeping settings), restart and reinstall.
If you install WinsCP for all users (as Administrator), you should not have this problem again in the future.

Thanks! I was afraid to uninstall it for fear I'd be unable to reinstall, so I tried half your solution: installing as administrator. That worked. Problem solved.