Key files ( actually key resources since it could be non-file resource data ) is expressed in the KeyPath column of the Component table. By clearing this out you specifiy the directory of the component is the default key file.
I'm not sure ORCA or the Direct Editor can do this in one shot so your best bet would be to use a script ( like WiSQL.vbs in the Platform SDK ) to issue the command
update `Component` set `Component.KeyPath` = ''
( I didn't check the syntax of the above but it looks right to me )