Let's backup here a minute ... is the installation to be a true server for production? or is it a tinker thang?
Reason I ask ... think you'd want to install it on an OS which has long term support (a server version of whatever) rather than a workstation OS. Please see:
http://www.networkworld.com/reviews/2013/120913-ubuntu-test-276581.html
"As with Ubuntu 13.04, Ubuntu 13.10 will only be supported for nine months. Prior to this year, non-long-term releases were supported for 18 months."
So if you are thinking server and you manage to get it installed and have it in production ... students enrolled and accessing/using, you will be looking at upgrading the OS in 9 months.
Another item that begs a question ... why put the DB on a Windows 7? Is that a DB server or is it the host OS in your VirtualBox virt? Gee, we are making a rather complicated system here!!! Think it *very wise* to keep things as simple as possible when first beginning any journey ... and Moodle is a "journey". It is not, never has been, install it once and forget it. It will require update and maintenace ... not only the code, but the parts that make Moodle go ... PHP, Apache, and MySQL (if sticking with a 'stock' moodle).
Truth in assisting: I run a Virtual Box on a Mac OS 10.9.1 laptop ... ubuntu server version.
http://www.ubuntu.com/download/server
with support guaranteed until April 2017
The Moodle on it was installed via git. DB server is on the same server.
OK ... to the current problem at hand ... one of the things about virtual setups is that one must allocate enough memory from the VBox to be able to run the OS + Apache/PHP and a 'heavy' app like Moodle 2.x. Let's also remember that installing a guest OS meant for GUI desktop means even more memory ... including video memory.
So how much memory does the host box have? How much memory/settings have you allocated to the guest OS right now? Yes, Moodle does launch ... but considering we're having issues with installing right now, even if one is successful in installing, think you'll be revisiting such issues during development of courses.
Firm believer in keeping things as simple as possible when beginning!
'spirit of sharing', Ken