If you are happy working in the registry, it is very easily done by navigating to
HKLM\SOFTWARE\Microsoft\Shared Tools\MSConfig\startupreg
There you will see all the unticked files, which you can examine and delete.
and
HKLM\SOFTWARE\Microsoft\Shared Tools\MSConfig\startupfolder
Little more care required with the latter, as it contains startup files installed by Microsoft. Mine are all unticked, so I removed them. But I do not reccomend it is you are experimenting.
- Delete any items listed in there that you no longer want shown unchecked in MSConfig