The Elecard watermark means you have the shareware version of the Elecard MPEG-2 Decoder on your PC. Some players, for example, WMP don't have their own MPEG-2 Video Decoder and have to use any installed. In your case WMP uses Elecard MPEG-2 Decoder. To get rid of the watermark you should either purchase the Elecard MPEG-2 Decoder and Streaming Plug-in for WMP or uninstall the decoder completely. To unininstall the decoder you should download this file: http://www.elecard.com/ftp/pub/mpeg/decoder/DecCleaner.zip
, unzip it and run ElecardDecoderCleaner.bat.
Keep in mind, that if you uninstall the Elecard MPEG-2 Video Decoder you will need some other video decoder instead of Elecard's in order to watch MPEG-2 videos. Otherwise, your WMP won't play any MPEG-2 videos at all. You can also buy Elecard MPEG player which includes the decoder.