Well, I'm trying to install SP1 on a Lenovo Thinkpad R61; and before anyone suggests it, I can't just clean reinstall with an SP1 slipstreamed disk. It's someone's work computer, and they need to keep the programs (they don't have the disks). Now, it fails at stage 3 of 3, 100%; "Service pack did not install, reverting changes". I looked around the internet, and found that the Windows Modules Installer service must be set to automatic. So I do so. But, it does not stay that way! Every reboot, it sets it back to "manual". Unless it;s set to "System" or "Boot". But that doesn't start the service, and anyway is likely to cause problems. I tried removing SYSTEM's permissions from HKLM\CurrentControlSet\Services\Trustedinstaller, but as I expected, it didn't work. Any ideas? EDIT: Okay, so it turns out that putting a deny ACL on the key actually prevented system from changing the key. However, despite being set to "automatic", it still doesn't start on boot. Anyone know if TrustedInstaller should have any dependencies? Or any other reason this might happen?