How edit XP registry from another partition?

I have the RTLgina.dll problem which means XP will not boot up, not even in Safe Mode. I know how to edit the registry to fix this, but without booting, cannot do that. The Recovery Console via the install CD lands me at the C:>WINDOWS prompt from which regedit does not work. I can access the XP partition from Vista on another partition, but do not know what file(s) to edit there, and how.