Its not a great program if you are looking for specific screenshots. This program just takes screenshots spread out at intervals through the duration of the avi.
For example, if you set the number of shots to 10, it will take 10 shots at evenly spaced times.
Example Screenshot of Dokuro Chan 01 (This shot has no editing done to it. This program set the screens up in this layout by itself):

Once you open ImageGrabber, click on the options and change the things you want to change. I only messed with the layout options, changing the columns and stuff.
To actually take the shots, open the avi file you want with image grabber. It will then start playing, without sound.
Click the Icon that looks like a TV. A dialogue will appear that asks how many shots you want. The picture above I selected 10. It will then go through the avi taking 10 shots.
Once that is done, click on the file menu and click "save file". Click ok through the first popup (its just asking what you wanted printed on the actual picture). Then save it to where ever you want.
If you have anymore questions, feel free to ask. I basically just played around with the program till I got what I wanted.