It's possible to have severe performance issues using VirtualBox on Windows. This is usually caused by Microsoft forcing their own Hyper-v hypervisor to startup with Windows in the background. This blocks direct access to intel's and AMD's virtualization on the CPU's. VirtualBox is therefore forced to fallback to Hyper-V, running all VM's as nested VM's on top of it.

This issue is indicated with a green turtle icon in the bottom taskbar of a started VirtualBox VM (as seen in the example image).