Alright, you can do it, it just takes a few more steps.
First download and install the latest Debian Wheezy ISO from here:
https://www.debian.org/releases/wheezy/debian-installer/
Note: Do not set the initial username as 'brewpi' use something else.
You can install a Debian desktop if you wish, I didn't and it still worked.
Once you are in at the Debian command line you need to do a few things to prep.
In VirtualBox go to the new VM and make sure the network adapter is set to NAT. There should be a port forwarding box somewhere (I'm on a Mac so it may be a button or a tab on windows), add a port forwarding rule. Add your Windows box's IP and the port you want to forward (I used 8888), then get your guest box's IP by typing 'ip add' on the command line of the guest box. Add it to the port forwarding rule, followed by the guest port destination (80).
Now when you set everything up, typing your Windows IP followed by :8888 will forward to the guest box's port 80. Example: My Host IP is 192.168.1.27 and my guest IP is 10.0.2.15, so I type 192.168.1.27:8888 and it will forward me to 10.0.2.15:80.
Then do this to make the setup of brewpi easier:
- Type 'su', enter the root password
- Type 'apt-get install sudo'
- Type 'adduser <your_username> sudo'
- Type 'exit'
- You should be back on the user command line, but now can use sudo commands
Now follow each step here:
http://docs.brewpi.com/manual-brewpi-install/manual-brewpi-install.html
If you need more help let me know.