Pray me my dear sir, could you share what OS are you on, what version of browser and what all did you do before the disaster chose to hit you with a disabled button. A screen shot would certainly be most valuable and also it may not be a problem with Registry at all - perhaps your parents chose not to let you play around with some sites as home page
I am not planning to tell you because it is very dangerous to modify windows registry. One wrong operation and you must lose your system actually, which is not my want.