bmp and gif aer not displayed

I’m totally new to Blender and I’m not sure if this is the right forum. Please tell me if this forum is not the right place.

I’m using Blender 2.65 on Win 7 (x64).
I try to create a video from an image sequence. I have no problems to import jpg images and create from them a video but I have problems with jpg and bmp image sequences. I can import them but they are not displayed on the screen and I cannot create a video from them.
Any idea why this is the case? Do I make something completely wrong?
Thanks for your help

In my experience Blender doesn’t display gifs. Convert them to jpeg or pngs.