Disclaimer: Running in Parrarel mode was not meant for Serious Windows Gaming. It might run but with terrible perfomance. The aim of this tutorial is for people who require Windows for Work. Afterall Steam Deck is a good portable laptop and way better then some standard corporate laptop.
So i got myself a steamdeck few weeks ago, I'm a casual terrible gamer who couldn`t live without the aid of TAS and Cheat Engine. The good thing about SteamDeck is there's 2 mode that you can choose, the gaming launcher or full blown Steam Desktop. There's tutorial here and there how to dual boot with windows which is fine by the way.
However I don't really like the idea dual booting and it kills productivity mood. So I look around for some tutorial on running Windows virtually and it's not documented properly. So here we go the tutorial in case i forgot.
On a positive note, dual boot works flawlessly means the SteamDeck is not designed with SecureBoot so mokutil hacks are not required.
Virtualization works quite well with SteamDeck just look at the supported flags:
How to install Oracle Virtualbox
In the Desktop Mode on your SteamDeck become root via sudo (be sure to setup password for "deck" username via passwd) and install the following stuff via pacman.
sudo steamos-readonly disable sudo pacman-key --init sudo pacman-key --populate archlinux sudo pacman -Sy --noconfirm --needed linux-neptune-headers gcc #Refer to Vbox website for the latest version wget https://download.virtualbox.org/virtualbox/7.0.6/VirtualBox-7.0.6-155176-Linux_amd64.run chmod a+x VirtualBox-7.0.6-155176-Linux_amd64.run sudo ./VirtualBox-7.0.6-155176-Linux_amd64.run sudo /sbin/vboxconfig sudo steamos-readonly enable
After you finished the VirtualBox should be available in the KDE Bar.