cant play videos

Long story short i was in desperation to get the vikings game in some form so i downloaded windows media player, VLC, and some other program called flip 4 mac. i then messed with quicktime settings to try to get a stream from a radio website. it worked, but now i get the quicktime logo with a ? mark on certain graphics on websites and it appears on you tube so i cant play the videos. i have deleted all the programs (i think) and restarted my computer. i also deleted quicktime and restarted. it still hasnt helped. please help me.
-Derek