i recommend bigasoft youtube downloader pro
with it, you can easily achieve:
Download YouTube video, music video in HD 1080p/720p, 3D or stand definition 360p/480p
Download video from all popular video sites like Facebook, Google Videos, Metacafe, eHow, Vimeo, MTV, BBC, Dailymotion, etc.
One-step download and convert YouTube videos and other online video to almost all popular video formats including MP4, AVI, MPG, WMV or HD MP4 (H.264, Xvid), HD AVI (Xvid), DV, ProRes, 3GP, MOV, MKV, VOB, RMVB and etc
Fast download and convert YouTube video, music video to all popular audio formats like M4A, WAV, WMA, AIFF, FLAC, AAC, MP3, AC3, OGG, RA, MP2 and etc.
Windows version at
link
Mac version at
link
Step by step guide on how to use it at
link