Comodo protects some of its files and keys so malware cannot kill it.
I think this is now done in Defense+
This protection can probably be cancelled before removing Comodo,
but I assume that simply un-installing Comodo should also notify Windows to cancel protection,
but if the system crashed during un-installation then keys may be frozen.
My daughter bought our laptop, and as sole user and administrator installed Comodo 2.4.
She subsequently passed this on to me and I became administrator with a new profile,
whilst she retained her profile but dropped down to User level.
When I upgraded Comodo there was no crash, but I could not update due to a frozen registry key.
This might have been a fault of Comodo, but Windows can trash its own registry without needing third party assistance. Perhaps Windows might have allowed removal had my daughter still been administrator.
This registry editor solved my problem, and should solve yours.
Registrar Lite - v 2.00 build 200.30803, August 2nd 2002
I obtained it free of charge from http://www.resplendence.com
Unfortunately this old version does not seem to be available from them now,
and the newer versions are more powerful at a cost,
or a bit crippled for the free versions.
It is however available fromhttp://www.majorgeeks.com/download469.html
That tool allowed me to see that the main Comodo key had about 2000 keys in about 6 sub-levels,
and two were marked RED and inaccessible and for that reason they could not be deleted and therefore the parent keys that contained them could not be deleted.
I selected the main Comodo key and right clicked for Properties,
and then I had buttons for Permissions and Take Ownership.
3 or 4 more clicks and I owned the lot and one more click eliminated them.
I forget exactly what I did and cannot test it because I am now tracking down a problem with my system.
Just be very careful and consider using ERUNT as a backup.
n.b. You can also right click keys with Windows RegEdit,
but that is a game of "blind man's buff" - so many ways to go wrong.