This is a deatiled tutorial on how to download youtube videos, If you have downloaded the youtube video and need to convert if from flv to avi please visit this tutorial here.
Ok so lets get started:
First off all find the video on youtube that you want to download and get the link.
Once you have copied the link head over to http://keepvid.com/ and paste you link into the box, and hit download
Now underneath the download button a new box should appear
Right click on the download link and click on save link as
Now choose you save location
And the download will begin
Wait for the download to finish and now you have downloaded your first youtube video!