I can't view html video on my computer when I had no problems before

What program are you using to view it? Adobe Shockwave? Adobe Flash Player?

I recommend that as a first step, you go to Add/Remove and unload Flash Player and Shockwave. Then go to the web sites and download the current versions:

Adobe Flash Player

Adobe Shockwave Player

Let us know if that fixed it. Also, if you're using Internet Explorer, go to Internet Options or Options (probably under Tools, depending on the version you're using) and locate the "Advanced" tab. There should be a button there labeled "Reset..." and the heading "Reset Internet Explorer settings". Click the reset button. If you're using FireFox or something else, let us know and we'll tell you how to reset that.