The simplest option would be:
If you're already using Firefox as your browser, then all you have to do is install the Video DownloadHelper
; this "addon" will enable you to download those flash videos and mp4s from youtube and similar sites.
Otherwise, download, install and use Firefox
as your browser, and then install that "Video DownloadHelper" addon.
Then finally, you'd also have to download and install some flashvideo (flv) player, or even better a complete media player and codec pack
, such as XP Codec Pack
. This is what would allow you to play different types of videos on your PC.
Happy downloadin and watchin.