Installing from CD/DVD-ROMs
In order to access CD-ROMs or DVD-ROMs, you have to make sure those are mounted on Linux first. In my setup, when I have VirtualBox running, discs don't automatically mount. This caused some confusion, as I was trying to install some Windows apps, which didn't mount automatically, and so when I tried to access them from Windows, it complained that the "disc may be corrupted." The disc wasn't corrupted; it just wasn't mounted!
I have one virtual machine, Vista, which is my installation of Windows Vista.
I'm using the non-free version, which has some additional support.
When I've played with VirtualBox in the past, in order to install my copy of Windows Vista, which is tied to the BIOS on my Dell Inspiron 531, I've had to configure the BIOS DMI, which I never bothered doing. No need with VirtualBox 3.0! Installation works out of the box. Yeah!
I did have one problem with Vista installation, however. Update returned Error Code 80073712. I found some suggestions on the Internet, and the problem was easily solved.
After successful installation, start the VM and install guest additions by going under Devices and selecting "Install Guest Additions." This will allow more seamless integration between Vista and Linux.
I also configured Shared Folders.
Virtual File Server
I experimented with another virtual machine, NAS, running Ubuntu server. I wanted to run this headless:
VBoxHeadless -startvm NAS &
I created and installed an init.d script using this script as a starting point.
It worked beautifully, but I realized it was unnecessary.
One potential issue was with disk size. I had configured a 750GB virtual disk, then realized that I didn't know ext3's file size limits. Turns out that for 4KB block sizes (which is what I have), it's 2TB, which was plenty for my needs.