All of the components in the operating system are found in the WinSxS folder – in fact we call this location the component store. Each component has a unique name that includes the version, language, and processor architecture that it was built for. The WinSxS folder is the only location that the component is found on the system, all other instances of the files that you see on the system are “projected” by hard linking from the component store. Let me repeat that last point – there is only one instance (or full data copy) of each version of each file in the OS, and that instance is located in the WinSxS folder. So looked at from that perspective, the WinSxS folder is really the entirety of the whole OS, referred to as a “flat” in down-level operating systems. This also accounts for why you will no longer be prompted for media when running operations such as System File Checker (SFC), or when installing additional features and roles. src: technet

I've been looking for this for a long time. On Windows Vista, there is a folder called "WinSxS", which stands for "Windows Side by Side". It's a part of the move to a "component" based architecture, where the WinSxS folder contains multiple versions of a component such as Windows Media Player or IIS, and the appropriate versions are hard-linked into the system. Unfortunately, Windows is stupid (surprise!), and provides no easy way to remove old versions. While it's understandable that users might want to uninstall updates for one reason or another, after the initial install it becomes pretty unlikely.

Now that Vista SP1 is out, there is a tool which will remove all of the RTM versions of updated components. Unless you plan on uninstalling SP1, there is no reason to keep these components around.

Cleaning out the directory is pretty simple. Click the start menu, and in the search field type vsp1cln. A single result should show up. I have UAC disabled on my system, so if it's an issue run cmd first, and run the utility through that.

I started with a WinSxS folder of 10.9 GB. After running the cleaning tool, it dropped to 8.48 GB - nearly 2.5 GB! While this doesn't matter so much on desktops, it could make a big difference in virtual machines, or on laptops.

It's too bad that there isn't a nice way to do this from a GUI. Hopefully SP2 will include one. src: abdevelopment.ca