How much video will a 4GB sd card hold?

It will depend on the resolution, length of the music video or movie and compression type which the video files use. e.g. For use in a pocket PC you can even have a full movie in AVI format which can be e.g. only 400MB per movie and that way you can have around 10 movies in a 1GB card. If your music video file size is 100MB you can have 40 of those in 4GB memory.

- Neeraj Sharma