VirtualDub could help you do that. Open your video file, and then go to File>Save image sequence. I think the default is saving the images as TGA.
When you are done, go to the folder where the images are, and change the "sort by name" so that the last image is now the first in the list. Rename all the files at once so their names come out in order.
Now go back to virtualdub, go to File>Open, select "Image sequence" in the file type and select your images. The video should be reversed. Go to Video>Compression and choose a codec for the video (make sure the video option is set to full processing mode) and save your avi!