I can't see any photos in "My Photo Stream" Folder

I opened up photo stream in my 4s(6.1.2),when I take some photos,I can see the new photos in the photo stream page on 4s,and I can see them in my MBA(10.8) and apple tv,but there aren't any photos sync into my PC(win7 sp1 x64),I reinstall icloud control panel(the latest version,2.1.2.8) many times,but still do not see that it will sync photos,please help me,thanks.