Not sure if anyone knows or has mentioned this but if you don't install a valid version of Windows 7 before 1 March 2010 then your Windows 7 RC will do a bi-hourly shutdown.
Windows 7 RC Details
I don't think you can get a pirated copy of Win 7 since its still in beta - all the product keys are pubic and valid
I know. What I mean is that the RC version of windows 7 will start shutting down every two hours until you install a non-RC version of windows 7.
EDIT: visit the link I posted and read under the section of "Here's what you need to know"