You shouldn't need flashget to download it, I did just fine without it. The MD5 verification is useless too.
Just download it without any flashget. You should get the install file. Open it up, do the yadayada and ECO should be set up within an hour or so (depending on the computer). If you had the wizard put a desktop icon on you can start ECO from there, or else you have to start it from eco_launch.exe from the folder.