May not be the right place but some videos that are posted on here has This plug-in not supported attached to them am I doing something wrong?
Yes the problem is at your end. You need to tell your browser which video plugin program you wish to use to view them. Can you view any videos? If the problem videos are on youtube then just google something like "youtube video plug-in not supported" and follow the suggestions given there. Otherwise ask any 12 y/o boy for help. They know these things intuitively these days :-)
If you are using Firefox, just go to the
Tools dropdown menu and select
Options, and then
Applications..
A new small window will open. Scroll down till you see the word
Video mentioned in the left hand column. Select the RHS of the line it's on.
The screen should look like the image below.

On my machine it was the third line down. Another smaller Window will open. Here you do your Plugin choosing. The problem may be that none has been selected. Select either
Realplayer or
Quicktime if they are not selected. Otherwise select the alternative plugin.
Other Browsers will have similar choices.
Good luck.