textarea to editer

Hi,
I want a plugin that can help us to change all textarea to editor. For example, In wordpress mainpage, “insert comment” is a text area. I want to this textarea to an editor. Eventually Wherever a textarea in wrodpress, i need to change it to an editor(i am mainly intended in user view pages not for wp-admin). I cant find any plugin for this needs. Pls help me to find out. or anyone use this (similar)plugin pls send me its code through replay
Rgds..