Hey 

I recently upgraded Windows 8 to 8.1. Unfortunately I left some hidden files in a folder in C:\windows\panther. 

The update seems to have removed and deleted all trace of this folder. Is there anything I can do to get it back?

Hi,

Based on my search, I found some articles about How to restore your personal files after you perform a custom installation of Windows. The article below applies to Windows 7, while you can have a try.

How to restore your personal files after you perform a custom installation of Windows:

http://support.microsoft.com/kb/932912

Retrieve files from the Windows.old folder(Applies to Windows 8.1):

http://windows.microsoft.com/en-us/windows-8/restore-files-upgrade-windows-old

Hope this helps.