That $&*^ WinSXS folder. Using up so much space, but not safe to clean up manually. Luckily in > Windows 8.1 and Windows Server 2012 R2 we have a way to shrink them a bit. Note: Run any of these at your own risk, have a backup, etc.
First, up the safe(r) option. Run this one to clean out previous versions of updated components (old patches).
Dism.exe /online /Cleanup-Image /StartComponentCleanup
Second, the more extreme version. This one removes the ability to uninstall any patches, so make sure this is a solid install first.
Dism.exe /online /Cleanup-Image /StartComponentCleanup /ResetBase