Classic Shell does not modify anything on the Start screen - files and settings related to Metro/Modern UI are untouched. Something else on your system damaged them. From an elevated (administrator) command prompt which you can open by press Win+X, run this command:
sfc /scannow
and restart Windows to see if the damaged files are repaired.
If sfc /scannow doesn't repair it, then try this:
http://winaero.com/blog/fix-error-14098 ... corrupted/The features you describe missing/damaged were added by update 1 (KB2919355). If above both steps do not fix the issue, open "Programs and Features" in Control Panel. Click "Installed Updates" and uninstall the updates KB2919355, KB2932046, KB2934018, and KB2937592. Then install these updates again. That may restore the damaged files.