I am attempting to install VirtualBox and failing miserably. I am brand new to Ubuntu (and Linux. Just started two days ago.) and want to install VirtualBox to run Windows 7; however, I don't know why it isn't working. I have tried installing it from Oracle's website. Didn't work. I tried uninstalling and re-installing. Didn't work. The main thing that is getting me is that I don't quite know how to properly install it. I have followed Oracle's instructions (I think) and when I try to install VirtualBox via the command line, I get this error:

Uninstalling modules from DKMS
Attempting to install using DKMS

Creating symlink /var/lib/dkms/vboxhost/4.2.6/source ->

DKMS: add completed.
Failed to install using DKMS, attempting to install without
Makefile:181: *** Error: unable to find the sources of your current Linux kernel. Specify KERN_DIR=<directory> and run Make again.  Stop.
Does anybody have any ideas?