I cannot use my registration key.Unfortunately, the problem that you describe is more like an internal one. I recommend that you to try your registration code later because whenever you buy a product before you enter the key, you need to wait until the validation process is ready. If you still have the same problem, the single solution you have is to get in touch with the developer and ask them to send you another registration code.
Fast YTD is a program that helps you download video from Internet. You can download one or more videos simultaneously. The program applies no restriction on the download speed of the video. so the video download will complete in less time and it automatically pastes URL's which you copied.