I should mention some possible improvements:
1) Program MDownloader takes on MS Win XP much CPU time and memory. Try find why and make some improvements. Now, I run MDownloader in priority lower then normal, it works.
2) Automatic recognition of captcha works often problematically. I propose option to switch automatic captcha recognition off and use only human recognition. If possible, individually for various providers.
3) When program needs user intervention - e.g. for captcha - generate some sound (like SystemSounds.Asterisk.Play(); ). The best with possibility of switching the function off.
4) For provider Letitbit the captcha consist of hexa listing of 3 byte number, ie. consists only from 6 digits and small letters a-f. Yout captcha recognition returns strings containing other letters. Test the recognised captcha for possile characters and
pass to provider the correct results only.
Program MDownloader is useful tool, but if you improve its properties, it would be better. Thank you for your good work.