I finally managed to install Windows Vista SP1. Hoo-flippin-ray!
I tried to do it about 3 weeks ago but after taking an hour to fail to install it then took another hour to roll-back the installation. I appreciated the fact that Windows still worked after the roll-back, but I was not exactly overjoyed at the installation failing.
After the roll-back I was presented with a dialog telling me the installation it failed (you don't say) and giving me a link to an article on Microsoft's Support site that was all about SP1 installation failures.
I ran the disk and memory diagnostic tools as recommended, but nothing came up. The real thing that solved the problem was "Resolution 5: Restart the computer and close or disable any applications that may be running". It recommends turning off anti-virus and anti-spyware, so today, when I finally had the time free to do it, I did just that and ... drum roll please ... it installed without a hitch.
I must admit (blush) that the initial installation instructions did recommend disabling anti-virus and anti-spyware, so I really only have myself to blame.
Well, now I'm using it and I'm hoping that the only bug I've hit so far will go away. The bug is that when I connect up to the network at work on a wire the first time I try to do something on the network (you know, something real complex like copying a file) Windows locks up. After I turn off and restart, the problem goes away. Also if I start up, wait for all the beginning activity to calm down and then do a restart, the problem does not occur. So, tomorrow at work I'll see what happens. Keep your fingers crossed.