My Video is TOO Fast!!!

Every time I play a video file … either mpeg, avi, or a divx, or even when I’m trying to watch streaming video online… it all goes by as if it were in fast forward.
I’m not a tech person at all, but I need desperate help. I’ve downloaded codecafter codec and installed and re-installed programs, and nothing seems to help.
am i just a loser?
also, .avi files have no sound. at least when i’m watching an .mpeg there is sound.

i just want to watch my favorite episodes of Upright Citizens Bridage, is that so wrong??