Is it possible to "virtualize" an existing PC?

It'd probably be easier to create a fresh VM, install Ubuntu on it, and then back up your dev box and restore the backup to the VM. That'd give you a VM you could run on any machine where VirtualBox is, or could be, installed.

That said, is there a reason you couldn't just open up VNC or SSH access to your existing dev box, and access it remotely? If possible, that might well be a simpler option -- at the least, it'd save you some suffering every time you want to use the dev box from a new machine.

Hope this helps!

you can dump your hd into an image with dd then convert the image to a vmdk or whatever.

apt-get install qemu (installs QEMU on debian/ubuntu)

qemu-img convert imagefile.dd -O vmdk vmdkname.vmdk

taken from: here