I cant open any file on my desktop everything is trying to be opened by windows photo viewer(win7)

first u scan the entire system with anti virus if there is no virus then select one picture file that is images or photos open the file format that file format should be identifed by u .if the file fomat is don't know then rightclick on the particular file andclick on properties,then it will display a new window
on that click on the change tab then it will open another a new window with recommended programs .after that select the windows photo viewer .cancel the tick button ,if it is ticked and it will be under the window and then click ok then u can easily solved the problem