Portable-VirtualBox is a free and open source tool that allow you to run any operating system from a usb stick without any installation.
Quick installation instructions
Download and run Portable-VirtualBox_v4.1.6-Starter_v6.4.8-Win_all.exe .
Choose a folder to extract to.
Go to the folder and run Portable-VirtualBox.exe .
All settings becomes automatically made. It’s nothing to edit manually.