I made the mistake of moving my Font folder from my Windows 7 laptop to my Windows 8.1 laptop and hitting "Install all."
Now some of the Symbols aren't appearing - for example the "Power" Symbol on the Start Screen.
Here are a few screen shots:
Mailbox: https://i.sstatic.net/qXVNw.png
Start Screen: https://i.sstatic.net/ZFID2.png
I'm assuming it is not as easy as finding the problem font and re-installing it - but if it was I wouldn't know which one to fix.
Any help is greatly appreciated.