Have you even tried searching through the Micro$oft site? They have numerous articles on the registry, it's repair, how to back it up, and how to restore it. There is a recovery console for XP/2000. I will assume you are using Win XP with NTFS file system, since you failed to give that detail. You should NOT try to write anything to an NTFS partition using Linux. It is too risky and can create more trouble on top of what you already have done. Don't try exotic methods before using some simple basic tools for Windows. BartPE can a also get you up and running again, since it can read and write to the NTFS partition more safely than Linux can.