If I disable the Windows Module Installer (TrustedInstaller) in the services panel, I get the same message as you when I try to run the System File Checker.You might check to see if it is set on manual and try to start it to see if it does. There is a way to run the SFC from offline, see the link.
How to Run the System File Checker (Sfc.exe) Offline in Windows 7 and Vista - The Winhelponline BlogYou can download and make a Windows 7 SP1 Install DVD to possibly do an Repair Install. The errors to which you refer, might stop this. But when you load the DVD, what error messages are you getting? And some information about your install might help.