I had about the same problem. The upgrade failed at 45% and the log did say something about IIS. But it had nothing with the fix. What I did was to remove all my USB devices. The last one was my USB WiFi adapter then the installation worked.
If you have any USB stuff or a card reader for an SD card or anything with USB. Try to disconnect them. That worked for me.
Thank you for the suggestion...
I have tried this... No luck.. it still fails...
Another friend has this problem as well.... So many have suffered with this problem for a while now.... It would be great if Microsoft had a utility to highlight the exact driver which is failing!