I understand fairly well how to create new commands for specific file types on Windows XP -- either through the Registry or editing the File Types on the Windows Explorer; in those cases, I tend to copy from existing options and adapt them.
However, I have not yet found a convincing way to reliably organize existing context menu items to unclutter an extensive Explorer context menu. For example, I'd like to be able to create a menu option "Source control..." where I could move existing context menu items for different SCMs installed on the system (Git, SVN, Mercurial).
I've tried some freeware software, but they didn't provide obvious solutions and some required the constant execution of a background process. Some have unusual interfaces, others do little more than hiding options, etc. So, some Regedit wizardry would probably be the desired implementation, although I'm willing to read alternative solutions.