I want to make an image with a transparent background, but each time I save the file (I've tried several file types) it fills in my transparency with white. On my other computer it saves as transparent with .gif format. Is there something wrong with my settings?

It won't let me change hue and saturation anymore also. I made some flaming text with hue and saturation changes, and after i saved that file, everything started messing up. I didn't change any settings.

I don't know if transpareny worked before then because I just tried it a few minutes ago. (This is a new computer)