With YouTube Downloader Suite you won't have to worry about that. You will be able to do searches directly in YouTube or enter the URL from YouTube as well as other servers like Vimeo or Dailymotion. With a simple click you can download the videos you want in various formats and qualities, even in 3D.
Furthermore, it includes a powerful convertor with which you will be able to convert the videos you download or any one in your computer, or put together a few videos in one, which is very useful for videos that are divided into parts in YouTube.
Evaluation version available for 3 days.