Windows media player opening files

Does any 1 know why Windows media player's trying to open my text files? How do I change it. And when I download files, it goes to a wmp looking file and wmp has to open it. For example, I dowloaded the ut3 patch, and when i go to open it, wmp wants to run it, which of course it can't. And, even when I going to download a file, such as 680i sli manual; the file icon it's going to be saved to is windows media player. I've tried rt clicking on the file and open w/ a different program but nothing opens it, and it changes all the files on desktop to open w/ the same program. I've tried running ccleaner, adware, and avast antivirus w/o any luck. I'm running vista 32-bit home premium. Please help.