Service Pack 2

Following a weekend of no web access due to home network issues, the connection was back today, and so I took the opportunity to download and install Service Pack 2 on the two machines in my study.
After spending an age making a backup of all the important data on my main machine I finally pressed the update button with a trembling finger. Everything went smoothly and it's working fine.
Not so the second machine! 3 hours later and it's still installing...