Oh, I thought you just meant C: windows in general, sorry. Have you tried cleaning up your Side by Side folder(WinSxS).:
To Clean the WinSxS Folders(using DISM)
Using Deployment Image Servicing and Management
Using DISM you can configure and update Windows features, packages, drivers and so on. The /Cleanup-Image parameter of Dism.exe, will provide you with advanced options to reduce the size of the WinSxS folder, writes TechNet.
A)Using the /StartComponentCleanup parameter of Dism.exe on a running version of Windows 8.1 gives you similar results to running the StartComponentCleanup task in TaskScheduler.Open an elevated command prompt, type the following and hit Enter:
Dism.exe/online /Cleanup-Image /StartComponentCleanup
B)If you use the /ResetBase switch with the /StartComponentCleanup parameter, you will be able to remove all superseded versions of every component in the component store. From the elevated command prompt, type the following and hit Enter:
Dism.exe/online /Cleanup-Image /StartComponentCleanup /ResetBase
C)If you want to reduce the amount of space used by a Service Pack, use the /SPSuperseded parameter of Dism.exe on a running version of Windows 8.1 to remove any backup components needed for uninstallation of the service pack. From the elevated command prompt, type the following and hit Enter:
Dism.exe/online /Cleanup-Image /SPSuperseded
Do note that if you carry out this command, you will not be able uninstall existing service packs and updates.