Why doesn't YouTube work on my computer at all?

Video wont work on my computer (HP with Windows 7) Please help?

• It doesnt matter which type of browser I use (Internet Explorer/Google Chrome/Mozilla Firefox/etc), no video will work on my computer. HP MediaSmart, Youtube, QuickTime, Hulu... basically any video viewing forum isnt functioning. The only fluke video I was able to watch was the iphone 4g video on Apple's website, and before I watched it, a pop up appeared asking to let QuickTime through my Windows Firewall. So maybe its a firewall thing? I changed some of my firewall settings to allow HP MediaSmart through but MediaSmart still isnt working. QuickTime didnt have a button to allow through, Internet Explorer did but I didnt know how much harmful stuff I would be letting through, so I decided against it. Maybe some other firewall setting? Internet Explorer as well as the other browsers are normal otherwise. I'm out of ideas to try to get it to work so any advice would be greatly appreciated! Thank you :)

• Answer:

  Try this: download adobe flash player and shut off any browsers before installing , also you can download and install k-lite codecs. I hope it will help:) By the way is your system 32 or 64 bit , because is important to choose right bit software.