I want to install Windows 7 RC.  I know about the time bomb in June of 2010, where it will cease to work, and that a few months before that it will shut down every two hours.

If I install Windows 7 RC, will I be able to upgrade it to a non-time bombed version?  If I pre-order the RTM, will I need to wipe clean and do a fresh install when it is released?