I'm using Windows 7 on a partition on my iMac, but my Boot Camp partition is running out of space. I use Windows for a particular subtitling program and otherwise use Chrome and Safari and printing. Is there anything in the standard Windows 7 installation that I can safely erase? I've tried to remove some useless movie files ín a folder called WinSat but am told that I "require permission from TrustedInstaller to make changes to this file". Anything to do about that?