In my experience, one of the most common causes of spontaneous reboots like this is bad RAM. If there is a bad spot in the RAM on your computer, then it will cause bad CD reads and bad Operating System installs. Have you tried using the memtest software that comes with every Ubuntu Linux installation CD or DVD? Just download, burn and boot up from an Ubuntu CD and run the memtest and tell us if it finds any bad spots in your RAM.
My favorite thing about OpenSolaris is that it will find bad RAM faster than any other operating system that I've ever used. It will always crash during boot up, or during OS install, or when downloading or uploading a large file, whereas Windows Server 2003 will run for months on the bad RAM before your web site gets popular and it gets hit with a heavy load and then leaves you suddenly wondering why it's spontaneously rebooting itself every 2 or 3 hours. -- This message posted from opensolaris.org
