Zenwalk linux is designed to be fast, lightweight and run on older machines (so it is less resource intensive).
That makes it an ideal candidate if you need to run Linux in a Virtual Machine like the excellent VirtualBox.
To install new software into Zenwalk, you need to run Netpkg, and you will probably want to install the VirtualBox guest additions to take advantage of mouse pointer integration. Before installing the guest additions, you will need to install the kernelsource package, which contains the headers you need when the guest additions installer tried to compile.
Do I have to specify in xorg.conf the drivers to use for display and mouse?