If you know what this directory is it’s probably because you tried to figure out where all the free space on your PC went…and found out the WinSXS directory was the culprit.

http://blogs.technet.com/b/joscon/archive/2010/08/06/should-you-delete-files-in-the-winsxs-directory-and-what-s-the-deal-with-vss.aspx