2 main ways to do it

1st way, (best way)
Open the file in Vegas or another video editor and render it in the "mov" format which is for QuickTime, then open the .mov file in ImageReady and save it as a Gif.
2nd way, (hard way)
[step one] open your video into windows movie editor
[step two] press 'take picture' ( on the right hand side, below the preveiw screen)
[step three] then press the 'next frame' (located under the preveiw screen'
[step four] repeat steps one to three, untill you have took a screen of every frame
[step 5] import the folder of screens in image ready
then your done