NEED help with IE8, no video stream

I'm hoping to get some new things to try, i have read and tryed many different things from different forums and nothing helps, i have a toshiba, i don't know much about computers, i did the update for IE8 and so far i cannot watch videos on youtube or yahoo, i also use mega video as a host site and cannot play those. on you tube i keep getting "an error has occured, please try again later" on mega video, it keeps saying "connection problem" and yahoo just does nothing. I am pretty sure the i have the flash player 10 activex

would downloading IE7 help? is that even possible to download an old version?