Should you ever encounter the problem where, upon starting up and not being able to get to the desktop because this message appears...
The User Profile Service service failed the logon.
User profile can not be loaded.
Here is a solution.
This occured on a laptop that had one profile, which was the administrator, and for which no password protect file was made.
Firstly, you need to start up and go to the Safe Mode options. Do not start in normal safe mode, for this will still require a password, and that is the problem.
What you need to do is open in Directory Services Restore Mode.
This will allow access to the desktop in a safe mode environment.
To correct the problem
Open the registry editor [REGEDIT] and go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList. There will be several entries, all beginning with S-1-5. Some will be short, and some long.
Look at the long ones, (in a format like S-1-5-21-xxxxxxxxx-xxxxxxxxx-xxxxxxxxx-xxxx.
There is likely to be two versions of each, one of which will have a .bak suffix.
Click on the one without the .bak and then click on ProfileImagePath. A message box will open and show the name of the user. This is to confirm it is the right user. You then need to swap this with the .bak version.
A set of renames will do it, change the non-.bak to .x, then rename the .bak so as to remove the .bak, then rename the .x to .bak. This will then allow the system to use the backup version. You now need to ensure the REFCOUNT and DWORD have the correct values. Double click on each of them, resetting to zero in both cases.
Close Regedit and restart. Et voila, you should be able to get in as per normal.
At this point, make a password backup !!!!!!!