|Try this :|
Basically, press F8 during startup before the winlogo comes up, and choose "last configuration that worked"
I have had this same problem. If the last known good configuration does not work you may have to reinstall the operating system. If you are running a raid or SCSI controller during set up it says to push F6 to load those drivers push F7 instead.
Practice makes perfect but only if you practice perfectly!