Everytime I click on multiplayer and press the button to join or create a game my computer freezes! Does anybody know how to fix this? If so please tell me how, thank you!

are you running windows 7 64bit?
When you say freezes, i assume you mean that you have to hold the power button for 5 secs or unplug pc to restart it (hard power down), thats right?
does this only happen when in mp?
does it happen instantly? or at a set time from start? or randomly?

Yes, I am running a windows 7 64 bit. And when the screen freezes, i do have to completely shut down the computer. It only happens in multiplayer when I hit find game when selecting Join internet game, or when selecting create a game. Once I select one of the two, the game and audio freezes (sounding like an orchestral disaster). And I have to restart the system. The strange thing is, I downloaded a campaign map, and it worked just fine.

I do not know why that happens.
I have had some troubles with win7 64 bit doing the same thing.
There are many articles on the net about it and none seemed to find a legit fix (or was not when i last searched)
It read something about winsoc, that maybe what your problem is, seeing as it only happens when starting mp.
http://social.technet.microsoft.com/Forums/en/w7itproperf/thread/7e8e0fc4-e24f-4e39-bc6b-769c86da1f5e
Edited by Maniac1000 on Jan 2, 2012 at 06:58 PM

I understand, thank you though, i appreciate your effort. Should I just re-install the game?

As a test (Only) try disabling your firewall then see if you can join a multiplayer game. If so then that is your problem and will need to open the correct ports.