In order to reclaim some space on a windows server hard drive, the contents of the “c:\windows\$NtServicePackUninstall$” can be deleted. All this means is that the current service packs cannot be uninstalled at a later date – no great loss if your server is running reliably. The files and folders within “C:\Windows\SoftwareDistribution\Download” may also be removed.
Do not touch the “c:\windows\ServicePackFiles” folder or the “c:\windows\$hf_mig$” folder! These include files that the operating system will use to update windows in the future. Stay clear!