Crusader works fine in dosbox.
Virtualbox has no additions for MSDos.
http://www.virtualbox.org/wiki/Guest_OSes
If you want a working VM for dos look for VPC2004@MS downloads.
It comes with the MSDos additions on a floppy image.
Install your MSDos in VPC2004, mount the floppy image,-(Dos Virtual Machine Additions.vfd)- run the dosadd.bat and you will have cd, mouse and SB-sound(220-5-1) support in it.
Works perfect.
BTW, the VPC2004 dos additions also works in VPC2007.