VirtualBox won't open. Error code 0x80040154

Solution 1:

You will have to uninstall that Xamarin player AND Virtualbox completely. Then remove all traces of both that may have been left behind (Revo Uninstaller is a good tool for that).
If you have a system-restore point dating from before you attempted to install Xamarin it may be less hassle to go back to that.
Reboot and then FIRST install Xamarin, then VirtualBox.
Oldest version FIRST.

It is possible that that combination doesn't work either. If that is the case you will have to again completely uninstall both and then decide which one you really need and only install that.

Please note: Because you have been trying multiple versions of VirtualBox without cleanly uninstalling any of them it is possible your Windows installation is already damaged to the point it is no longer possible to get back into a clean state. If that is the case you hopefully have a restore point dating from before the time problems started. If not a re-install will be needed...

Solution 2:

I actually fixed it... all i had to do was delete the ".virtualbox" folder in "C:/Users/"User"/.Virtualbox:(replace "User with your account's name"

thanks for the help guys. I really appreciate you guys giving me advice.