Hey Microsoft: please learn how to do this invisibly in the background without needing any rebooting:
More from: reboot
Apparently a significant number of people who have tried to upgrade from Vista to Windows 7 instead of doing a disk wipe and clean re-install are finding their computer locks up in a continuous reboot cycle: the install fails and then the computer reboots, the install fails and so forth. We only do clean installs, so we did not test this mode.
In a similar trouble report last July Readmore..