This is the i386 install CD of Ubuntu 6.06 Flight/Alpha 6. This was the first milestone to be called 6.06, as the schedule was revised just over a week before this build. It's quite an interesting build, with a lot of differences to be spotted from both 5.10 and 6.06. GNOME 2.14 final and an updated version of the Espresso (now known as Ubiquity) installer were the highlights of this release compared to Flight 5, though the latter can't be seen here.
This build's installer has a pretty serious bug preventing you from installing the full OS normally. It manifests as a stall when trying to load the desktop packages from the CD, preventing the install from successfully finishing. However, it is possible to get around this by installing the base OS first (select "Install a server" when booting from the CD), then running the command "sudo apt-get install ubuntu-desktop" after logging into the terminal for the first time. The packages should then be loaded and installed successfully, and on rebooting, the install will work exactly like a normal install. Have fun!