It took me more than a month to muster enough courage to try again -- and this time, it all worked on the first try! I really need to find another solution for the case fan, though -- that has replaced the CPU fan as the loudest component in my computer.
I decided to install SP2 while I was doing maintenance on my system anyway. That takes... quite long. I read quite a lot while waiting for the process to end. Now everything is up-to-date, and that makes me happy.