I transferred Windows XP to another machine (I called it my "total hardware upgrade"), and at the time, my research showed that Windows will allow a certain number of reinstalls when you haven't changed too much hardware. I think it has a point system, and each hardware change gets assigned some value. MB is pretty big though.
Anyway, I didn't have any problem... you will probably need your license # though. And if you still can't fully install, a call to Microsoft will usually fix it.
Also, I'm pretty sure it will successfully reboot, but you'll get a warning message about your license, and will have a limited number of reboots before it will lock you out...
(all from memory from when I did it many years back...)