About the resetting clock, I had that when my pram battery was running low (actually after a power surge). What sort of mac do you have? If it's a powermac they're easy to replace. There's probably lots of other explanations, but that's just what happened to me.
Oh, and like analogika said, when you drag a picture to the desktop it should save as whatever is the picture format. If it is a picture clipping, try opening it, choosing copy from edit menu, and then open Preview and choose new image from clipboard from the File menu.