In software development terms, Release Candidate is the final stretch. The first Service Pack for Windows 7 is pretty much all the updates released so far collected in a single package, plus improvements to virtualization and remote desktop use...Service Pack 1 will bring Windows 7 computers up to date if their auto-update was off all this time (some companies do that in their offices, in case some update turns out to be faulty). The two new things that SP1 brings are RemoteFX and Dynamic Memory.