Windows: Clear Disk Space

Left to its own devices, Windows will happily fill up whatever drive you put it on. Latest versions are better, but still leave unnecessary bloat around e.g. Windows Updates. Cleaning up these files is particularly important when you are running virtuals.

Where Is Space Being Used

Use a program like TreeSize Free to find where your space is used up.

Clean Up Disk

Use "Disk Cleanup" program included in Windows to clear space on drive C. 

NB You'll need to run it twice: once as normal used, then select 'Clean up System Files' to run it again and review the options.

Clean Up WinSxS

Windows keeps removable files in C:\Windows\WinSxs which is often quite large.
Using a command prompt as admin:
Dism.exe /online /Cleanup-Image /StartComponentCleanup