Enable Network Adapter

[Cachi]

I would like to be able to use the web browser (Firefox) from within the VM CentOS 4 (VM VirtualBox Manager screenshot: //cl.ly/image/2m3i0Y333507 )

Note: please add h-t-t-p: in front of the links (since this is my first post, I'm not allowed to post links)

Here are the default settings of the Network tab screenshot: //cl.ly/image/3d140l340g26
I don't know why the "Enable Network Adapter" checkbox is grey'd out (as are other features/functions throughout the VBox Manager)
I have tried different settings (without restarting the VM though after each change)

OS X 10.7.5
Oracle VM VirtualBox Manager V4.2.12

I would appreciate any help you can provide

Thank you

[noteirak]

You may not be allowed to post urls, but you are allow to attach files to the topic.