Prior to win7, the system builder EULA used to say its meant for assemblers and manufacturers and not for the end user UNLESS the end user actually assembles his own rig. But in win7, that crucial part has been removed and now as per the EULA, the system builder license can only be used on a PC meant for resale. So technically it does appear you would be breachibg the EULA by installing it for personal use.
However, let me state at the risk of annoying some people that here again there is a gap between idea and practice. System builder copies are freely available at respected stores, if MS didnt want them to be there, they wouldnt be there. MS doesnt care whether you are an assembler or not provided you buy a genuine copy and install it on a single computer.