The list of engines is stored in the ENGINEEXT.INI file, to remove an engine from the list simply edit this file and remove the complete section starting with:
EnginePath="C:\Program Files\Lokasoft\Engines\Some engine\SomeEngineexe"
The location of this file depends on the version of ChessPartner, in 5.x versions this file is in the windows directory, in 6.x its under
You can also open this file via Extra -> Engine properties.. – Edit profile
More info about the ENGINEEXT.INI file here: