In the company that I work, we have Windows 7 installed on all PCs. We don't have internet access through Windows but can set proxy settings in Firefox and can thus access the Internet.
I installed a virtual box on one of these Windows 7 machines and Ubuntu 14.10 but I have problem with accessing the Internet.
How can I access the Internet through the proxy server via an Ubuntu virtual box running under Windows 7?
you have to make a Network Bridge in Windows (between VBox Host-Only Network and the Controller connected to the Internet)
In Virtualbox you can leave the Adapter at NAT
I´m using this with my debian-vm. Additionally I added the Network-Proxy as system-wide Proxy in my VM.
I think you can use Bridged network mode on your virtual box. Then assign IP address for you ubuntu to connect to your network, and then use the proxy setting at the ubuntu's internet browser.