I honestly have no idea what problem you are facing, but it OneCare is crashing, you may have a conflict. Based on the fact that you also mention a registry cleaner, I suspect that your problems with the PC run deeper than just OneCare.
See this post for the KB article to troubleshoot install problems - http://social.microsoft.com/forums/en-US/onecareinstallandactivate/thread/ba26b781-da18-4ce4-be8c-22647bd5d8fc/
-steve
Microsoft MVP Windows Live / Windows Live OneCare, Live Mesh, & MS Security Essentials Forums Moderator