I installed Ubuntu guest on a Windows 7 machine using VirtualBox. How can share folders between Ubuntu guest and Windows host? Thanks.
Close out your guest VM, and then open up the Settings dialog for that VM. Down near the bottom of the left hand navigation area in that dialog should be an option for shared folders.
You can select which folder(s) on the host machine you want shared with that particular guest VM, whether you want them mounted read-only by the guest, and whether to make them available on boot of the VM. Once done, restart / restore the guest VM and you should be able to navigate to the new filesystem or folder.
I usually make a new folder inside the 'VirtualBox VMs' folder in my user directory, titled 'Shared' and then share that folder with any guest VMs that need it. I mount it read-only so that no one machine can b0rk it for the others, and then I can place any necessary files in there that are desired.