Do you have an icon on your desktop for dkonline? if so right click it and choose "open location", that will take to the folder that should also contain the folder "downloader", in that folder if you turn on "details" for your folder view you should see a file that is over 3 gigabytes in size, double click that file. create a shortcut from the new dkonline that appears and send it to your desktop or wherever for easy access.
If you still can't find the massive 3+ gigabyte file, get a file structure viewing program such as WinDirStat found at http://windirstat.info/
and let it analyze your hard drive. In a moment it'll pop up and show you multicolored blocks of varying sizes, at 3.7 gigs I'd say the largest or the 2nd to largest block will be the file in question. It also gives you the name of the blocks when you hover over the blocks.
Video of WinDirStat in use. http://www.youtube.com/watch?v=uikCLZcw6W0&feature=related