"open with" problem please help!!!?

I opened a pic with 'paint' by right clicking on it and selecting 'open with' then 'choose default program...' then 'paint' but i didn't uncheck 'always use the selected program to open this kind of file' so every thing opened with 'paint' and i realized this and tried to fix it myself (stupid move) and did the same thing but instead of 'paint' i selected 'vindicus launcher' (it's an online multiplayer game)so how do i undo this so that everything opens as usual?!?!???!?!? pleeeeeaaasssssssseeee helpp meeeee!! DDD":