All credit to Mark Parris (@markparris) for this one, http://markparris.co.uk/2011/04/12/clean-up-after-installing-service-pack-1-on-windows-7-and-windows-server-2008-r2/. I thought it was really useful (for me in the future) so wanted to post here.
“After installing Service Pack 1 on Windows 7 or Windows Server 2008 R2, by default you have the ability to uninstall the Service Pack and rollback to the previous state. If you are confident that you do not need to rollback the service pack at a later date. The installation can be made final by running DISM /online /cleanup-Image /spsuperseded on average this has reclaimed for me over 2GB per server, not that much space these days but if you have for some reason VM’s running like this, these 2GB’s can add up to a lot of space.”
DISM has some great features including upgrading Windows Standard to Enterprise, its all covered here http://technet.microsoft.com/en-us/library/dd744256(WS.10).aspx.
Daniel Noakes