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:

[Some  engine]
Console=1
EnginePath="C:\Program Files\Lokasoft\Engines\Some engine\SomeEngineexe"
EngineDir=
… etc.

 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

%programdata%\lokasoft\chesspartner6.0

 You can also open this file via Extra -> Engine properties.. – Edit profile

 More info about the ENGINEEXT.INI file here:

http://www.lokasoft.nl/engineextini-file-layout.aspx