Thanks for the posting, I don't use task scheduler or windows defrag myself but I just checked this out and it's true that all options in the task scheduler services are greyed out and running defrag appears to do nothing but show the UAC screen.
I have a drive set up, which I can choose from bootup by tapping F8 at the appropriate time in the boot process, which I use to test updates and the like before applying them to my main drive. On trying the .reg file you supplied the link to on this test drive it doesn't appear to have fixed anything, other than perhaps allowing the computer to run the service on startup on machines where the service has been switched off. On my test drive the task scheduler service is set to automatic but I'm still unable to alter any settings and the defrag still doesn't appear.
Did the "fix" allow you to alter the task scheduler service settings or allow defragmenter to work after you applied it?