In the reboot loop since Tuesday night. Automatic updates are turned off, but that doesn't not seem to stop them.
This is where get into "where did I put that system recovery disk I made five years ago?"
I can get to startup repair, which fails, and to the screen for choosing repair modes, where neither "repair system disk," "go back to an previous system image" nor "restore to OEM system image" will work.
I can boot and run an Ubuntu 10.4 from DVD image, where I can get to the Linux disk utilities and could once see the internal drive with undamaged file systems, mount the partitions and look at the files.
After a few more startup repair attempts, Linux no longer finds the drive on the SATA controller. This is a Dell XPS 8300, a model known to have a fault in the chipset, statistically small risk of intermittent failure of SATA interface to the bus. Early examples got a motherboard replacement, this example was supposed to have been manufactured with the corrected bridge chip.
This is the second time this year an update has failed, last time I got it repaired to bootable and backed off the updates.
I think my next "power" computer for photo editing and video production is going to be an iMac, as right now they are selling for a lot less than what someone else wants for a good IPS monitor and XPS-class box with equivalent processor, memory, storage and less capable graphics. A leap of faith, since I've not used a Mac since the Mac II in my Unix workstation test lab twenty-some years ago.
Decision partly driven by my collection of dead Dell computers (three Inspiron laptops, three desksides including two in "workstation" class). Three of the six taken out by disk controller failures.