FD,
Thanks for the link with DISM /online /Cleanup-Image /SpSuperseded - that does work in Win 7 and reduced the Windows footprint by 1GB.
However, it's a one shot deal, as it is only able to remove the service pack files, and since there was only one SP for Win 7, that's your lot.
It's interesting to look at the system partition sizes on Windows NT over time - starting with NT3.5.1 and NT4 there was a hard limit of 7.8GB and an effective limit of 4GB - more than adequate, ISTR! The typical sizes for deployed servers that I saw in a large number of companies for the various versions of Windows since then were along the lines of:
Server 2000 10-15GB system partition (= Win2K), often less
Server 2003 20-30GB system partition (= Win XP) - I recently saw one with only 10GB that had been a major pain for several years
Server 2008 40-60GB system partition (= Vista) - once bitten...
Server 2008R2 60-80GB system partition (= Win 7) - ...twice shy!
Server 2012 & R2 80-100GB system partition (= Win 8 & 8.1) - to prevent the problems seen with 2008!
This is what I mean about the inexorable rise in the size of Windows OS, although of course a lot is also due to the size of application software as well.
I'm not expecting that trend to stop rising, although it would be good to think that it is flattening off somewhat!
SD