SBS2003 SP1 was successful - ultimately
The days between Christmas and new year were going to be the days I caught up with a heap of things in the office that had not received the attention they deserved through the rest of the year. Instead I was busy by a few clients that simply refused to take some time off :)
Anyway, I did manage to get SP1 finally applied to our own server, in readiness for CRM 3.0 (see previous post). Overall the installation when fine, apart from the ISA2004 upgrade. Now don't get me wrong, our SBS2003 server is not overly customised - we built our own server the same way we build them for our clients. Makes it easier to support overall.
So each time I went to install ISA2004 as an upgrade from ISA2000 it would complain and roll back the installation. I ended up manually uninstalling ISA2000 (remembering to export the self-signed certificates first) but still had problems. Evertime I went tp stop the IISADMIN service and its dependant services it would start up again.
To make a long story short, I had to change the recovery settings for the service. It was set to restart on first & second failures and on subsequent failures to run "iisreset". I changed all of these to "no action" and tried again - this time I was successful. (I remembered to set the recovery options back afterward).
So if you're rolling out SBS2003 SP1, or even just upgrading ISA2000 to ISA2004, watch for the service recovery options on IISADMIN. Hopefully this will serve to save you a little grief.