Your getting these errors because like I said. build 7127 is from the RTM branch.. it is NOT another RC build..

Therefore, upgrading is NOT a good idea.. A clean install is the way install build 7127..

As for fooling Win 7 into letting you upgrade.. you may be able to but it's just not worth it.. Clean install takes 14-15 mins (via USB drive) vs whatver retarded amount of time it would take you to work around those errors..
The differences between the RC and builds 7127, 7130, 7140 (ALL from the RTM branch) are so far negligable.. I wouldn't bother installing them.. The RC works fine and is very stable... If you've got your system running near perfect then I wouldn't mess with it by installing another build that honestly doesn't bring any major changes to the table..