When installing the November CTP of the WinFX Runtime Components, I consistently encountered a problem. I experienced a hang of the setup.exe process at about 90% of the Loading Setup Components stage. The process took up all the available CPU and the most annoying thing of all was that the process could not be killed. The only way to return my computer to a usable state was to reboot. After about three attempts I decided to dig a little deeper.
I remembered reading a blog entry of Mark Russinovich about unkillable processes. So I downloaded and installed the latest Windows Debugging Tools from Microsoft and LiveKd from Sysinternals. The offending thread in the setup.exe process had two outstanding I/O requests in the IRP list that had not completed: one in AFD.sys and one in tcpip.sys. Since both have to do with networking, after another reboot I disabled my Kerio Personal Firewall and my LAN connection. This time the WinFX setup process passed the problem point. I re-enabled my TCP/IP connection when it wanted to download additional components. Setup completed without further problems.
Thanks Mark for the great tools and blog entries that help diagnose and fix these kinds of problems! Although I don't know what the root cause of the problem is, I can play with the latest WinFX.