"Pre-releases of Intrepid are *not* encouraged for anyone needing a stable system or anyone who is not comfortable running into occasional, even frequent breakage. They are, however, recommended for Ubuntu developers and those who want to help in testing, reporting, and fixing bugs.

Alpha 4 is the fourth in a series of milestone CD images that will be released throughout the Intrepid development cycle. The Alpha images are known to be reasonably free of showstopper CD build or installer bugs, while representing a very recent snapshot of Intrepid. You can download it here:

http://cdimage.ubuntu.com/releases/intrepid/alpha-4/ (Ubuntu)
http://cdimage.ubuntu.com/edubuntu/releases/intrepid/alpha-4/ (Ubuntu Education Edition)
http://cdimage.ubuntu.com/kubuntu/releases/intrepid/alpha-4/ (Kubuntu)
http://cdimage.ubuntu.com/xubuntu/releases/intrepid/alpha-4/ (Xubuntu)

See http://wiki.ubuntu.com/Mirrors for a list of mirrors."