If you launch Minecraft and get an error as above, along the lines of cannot copy file error code 5 then you can potentially fix this by renaming a file as below.
Rename
C:\Program Files (x86)\Minecraft\tmpLauncher.tmp
to
C:\Program Files (x86)\Minecraft\minecraft.exe
Then just run the minecraft.exe file and it should start to download the runtime and then start up. Worked for me 🙂