When starting your computer and receive this error "The User Profile Service service failed the logon. User profile cannot be loaded" dont worry, its an easy fix.
1. If your able to log in as admin, go ahead and do so. If your not able to log in as admin, boot into safe mode.
2. To boot into safe mode, on boot up, hit the F8 key consecutively with about 2 second intervals in between.
3. Once in safe mode, it should allow you to log in to the problematic profile.
4. Open the registry. To open the registry, click on start, in the search bar and type REGEDIT
5. You will see a window just like the one below.
6. Navigate to HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows NTCurrentVersionProfileList
7. You will see a list of registry entries and some with .BAK
8. Save registry before you continue editing any further.
9. You should see 2 of the same entries one with .BAK and one without.
10. Rename the one with without .BAK to old or something distinctive
11. Remove the .BAK from the other one.
12. Log off then back on.