Problems with icons and accessibg programs [Closed]

I was doing some self tutoring by getting to know systems n programs. Exploring properties somewhere along that exploration I've changed something, now all icons are the same and the programs can't be accessed through hitting the icons. Programs still operate I have to click on a file and option open with to use them though. Please help me find out what I changed and how I change it back. I can change the icon but it changes them all and still can't access programs that way. Err its really annoying. Help please