I have had Limewire for quite a while and I am very happy with it. That is until the other day when I tried to play a vidoe I downloaded. Nothing. I have no clue as to why. Does anyone have any ideas? Please help!!!!!

Which player are you using? Try VLC player, if VLC won't play it then you might've downloaded a fake.
Codecs & VLC

Always look up a file with Bitzi before download
How to use Bitzi

it is definatly a codec issue.. i had the same problem like 2 days ago with avi and mpeg-4 files.. among others.... try searching goole for a player/codec called DivX its excellent and very pospular among the media creators online right now... it fixed my problems right off!!
hope it helps

Thank youso much for the help! If I can help you someday just let me know!