well, you do need similar processors, of the same frequency and same stepping to work together. you might buy two newer processors in exchange for the current one, but be sure both have same frequency and stepping.
you wont need to reinstall windows nt, it will automatically detect the new hardware and run a routine or two to update its profile and might reboot once. thats all.
<font color=blue>die-hard fans don't have heat-sinks!</font color=blue>