perhaps you can try this? install videocacheview, a freeware that allows you to view media/video files in the browser's temporary cache and view the video offsite. there's a portable version. please take note that not all youtube videos will appear in the cache folder even if it's fully buffered. also, videocacheview doesn't show the name of the video but assigns it a temporary name. i just set it to show videos accdg to date/time modified and just try to remember which video i opened first. ;D also, the video tab has to remain open in the browser for VCV to keep track of the vid.
you can then click on the video and either choose to play or save the video in any folder. pls note also the video cached is in tmp file format. but if you make daum potplayer as your default video player, it can play the video automatically, no problem. potplayer also allows you to view the video in various configurations: right click > video > pan and scan > then choose your setting. tho the results may not be entirely to your liking.
you can also just download the videos. i use flash video downloader or complete youtube saver which are firefox add-ons (no need to install software). (sorry i can't post links. im a newbie and not allowed to post more than two hyperlinks)
if you pin videocacheview and potplayer on the taskbar, it's at most a two-click process.