When you login to your user account, the Start menu may pop-up automatically, and the Most Frequently Used programs list in the Start menu may get reset with the factory default list.
This happens if the StartMenuInit registry value is not set correctly in the registry. During the first logon to a user account, Windows is supposed to set the StartMenuInit value automatically. If that procedure fails for some reason, then Windows resets the Most Frequent Used programs list with the factory default programs list automatically at every logon, and pops up the Start menu automatically.
HKEY_CURRENT_USER \ Software \ Microsoft \ Windows \ CurrentVersion \ Explorer \ Advanced