Well, thank you to all who have responded .. unfortunately the problem is not yet resolved.
Using run/browse .. I located and right clicked the .reg file and merged it in again.
But that did not solve the problem. Run explorer.exe gives me the same issue as
when I try to use "my computer".
I think a system restore might be the only way to get it back, but I am unsure as to how to do it,
and am unable to get into the Control Panel.
Can someone step me through how to restore the system?