Recently following a clear out of my Windows 7 64bit laptop and running TreeSize to locate offending large files and folders, I found a 6GB folder called WinSXS. Not having a clue about what this folder was, I decided to investigate..

First of all “Can I delete the \Windows\Winsxs directory?”

To answer the question, the answer is actually: No.

Why?

Because the component store (\Winsxs) is needed to repair the OS binaries in the event that a file becomes corrupted or, in worst case scenarios, compromised.  There are a few directories in the component store so let’s look at them and what their general role is in Windows. WinSxS folder replaces the old $NTUninstall folders from XP which is one of the reasons it grows after installing Updates

1. \Winsxs\Catalogs:  Contains security catalogs for each manifest on the system
2. \Winsxs\InstallTemp: Temporary location for install events
3. \Winsxs\Manifests: Component manifest for a specific component, used during operations to make sure files end up where they should
4. \Winsxs\Temp: Temp directory used for various operations, you’ll find pending renames here
5. \Winsxs\Backup: Backups of the manifest files in case the copy in \Winsxs\Manifests becomes corrupted
6. \Winsxs\Filemaps: File system mapping to a file location
7. \Winsxs\<big_long_file_name>: The payload of the specific component, typically you will see the binaries here.

Explanation

The Windows component store (C:\Windows\winsxs) directory is used during servicing operations within Windows installations.  Servicing operations include, but are not limited to, Windows Update, Service Pack and hotfix installations.

The component store contains all of the files needed for a Windows installation and any updates to those files are also held within the component store as they are installed.  This will cause the component store to grow over time as more updates, features or roles are added to the installation.  The component store utilizes NTFS hard links between itself and other Windows directories to increase the robustness of the Windows platform.

The component store will show a large directory size due to the way the Windows Explorer shell accounts for hard links.  The Windows shell will count each reference to a hard link as a single instance of the file for each directory the file resides in. For example, if a file named advapi32.dll was 700 KB in size and was contained in the component store and the \Windows\system32 directory, Windows Explorer would inaccurately report that it consumes 1400 KB of hard disk space

The component store cannot reside on another volume other than the system volume due to the use of NTFS hard links.  Attempting to move the component store will result in the inability to properly install Windows updates, Service Packs, roles or features.  Additionally, it is not recommended that files be manually removed or deleted from the component store.

To reduce the size of the component store directory on a Windows installation you can choose to make the service pack installation permanent and reclaim used space from the Service Pack files.  Doing this will make the Service Pack permanent and it will not be removable.

To remove the Service Pack files from a Windows installation use the following in-box utilities:

• Windows Vista Service Pack 1 installed: VSP1CLN.EXE
• Windows Vista Service Pack 2 or Windows Server 2008 Service Pack 2 installed: Compcln.exe
• Windows 7 Service Pack 1 or Windows Server 2008 R2 Service Pack 1 installed: DISM /online /Cleanup-Image /SpSuperseded or Disk Cleanup Wizard (cleanmgr.exe)

Scavenging may also be proactively performed on Windows Vista and Windows 2008 installations by forcing a removal event on the system.  Scavenging will attempt to remove any unneeded system binaries from the installation and allow Windows to reclaim the disk space.  To issue an uninstall event on a Windows installation, simply add and remove any unneeded system component that is not already installed and reboot the Windows installation.  Scavenging will be performed during the subsequent reboot of the operating system.

NOTE: Scavenging is performed automatically on Windows 7 and Windows 2008 R2 installation