To load Mac OS X via "Safe Boot", hold shift as the system reboots. A message should appear in the progress window indicating the alternate booting mode. This does several things:
- It forces a filesystem check of the startup volume.
- It loads only required kernel extensions (some of the items in /System/Library/Extensions).
- It runs only Apple-installed startup items (some of the items in /Library/StartupItems and /System/Library/StartupItems - and different than login items).
If you hold the shift key while logging in, it will disable all of your user's login items.