To download videos from sites like youtube.com megavideo.com metacafe.com e.t.c.
All you have to do is
Follow the following steps

Step 1: Open Internet Explorer

Step 2: Go to that site

Step 3: Watch the full video

Step 4: Replay it one more time just to make sure that the whole video is buffered into the memory

Step 5: Go to The Desktop and right click on the internet explorer icon

Step 6: Click on Internet properties.

Step 7: In the General tab of the Internet properties dialog box you will find a Temporary internet section click on the setting button of that section

Step 8: Then a setting dialog box will appear Click on the View files button.

Step 9: Then a window with detailed view will open there click on the size tab to find the file with largest size (or just right click on the window and arrange icons by size) the file with the largest size(in mb where most files are in kb ) will be your video file

Step 10: Then just copy that file in the desired location (e.g. desktop) and rename with any desired name and extension .flv

Follow the given steps and you will get any videos from any site you like