To download youtube videos, you can use uSeesoft Free YouTube Downloader. download: http://www.useesoft.com/products/useesoft-free-youtube-downloader.exe
It can help you download YouTube videos with fast speed. This tool is easy to use. You can add direct URL of YouTube video which you want to download and then click “Ok” button to start downloading.
If you want to convert youtube videos to avi, wmv, etc. files, you can use uSeesoft FLV Converter from this page http://www.useesoft.com/video-converters/flv-converter.html
It can convert YouTube videos or FLV videos to other video or audio formats, such as converting flv to mov, mkv, avi, mp4, mp3, wav, aac, etc. Specially, it provides an easy way to convert YouTube videos or FLV videos to iPod, iPod Classic, iPhone, PSP, Apple TV as well as other portable video players. Hopefully you will have a try to convert or edit youtube videos.