'Installation' window shows up again, is it not portable?

[Kotsuha]

I downloaded the Portable-VirtualBox on a Win8.1 machine, went through the 'Installation' process, and used it for a while. Now I copy the whole folder to a USB stick, bring it to a Win10 machine. When I run the Portable-VirtualBox.exe, the 'Installation' window shows up again.

Q1: Am I doing it wrong?
Q2: Because the 'Installation' window shows up again, it seems that it's not truly portable? Does it install VirtualBox to somewhere else outside of the 'Portable-VirtualBox' folder? If so I would like to know where the location is.

Thank you.

[Kotsuha]

I just found out that it's not the problem with copying to a USB stick. It seems that I can't use Portable-VirtualBox on that Win10 machine. I tried to download a brand new Portable-VirtualBox directly on that machine but still couldn't use it. In the 'Installation' window, after I clicked 'Download installation files of VirtualBox', the download started, and nothing seemed to happen after the download finished.

I then used the installer version instead and it worked well.