Many find their installation goes into infinite reboot after 62% of the installation is complete. Switching off and rebooting doesn't help either because the system no longer recognizes the older operating system.
Microsoft said the problem occurs because the Iphlpsvc service stops responding during the upgrade. But others may also be to blame.
One user who followed Microsoft's fix said it took 48 hours to get a working installation, with installation runs taking 10 hours a time. Even then he had to delete his wireless card and get the operating system to find it again.