It's my own fault really, but, while installing our software on a client's machine, I attempted to install .NET 2.0 framework and XP Service Pack 2 at the same time. I started the Service Pack 2 installation first, and the 2.0 framework installation completed successfully, but the SP2 installation hung when it was installing FXSAPI.DLL. Task Manager did not open up, and new windows would not open up. Existing windows would work, and I could browse the internet using an already open instance of IE. After waiting 15 minutes for something to happen, I manually reboot the machine. The system restore kicked in and it reverted back to SP1. I restarted the SP2 installation and everything worked well.