The User Profile Service service failed to login.

How to fix the Windows Vista and Windows 7 error:

“The User Profile Service service failed to login.

User Profile cannot be loaded”

This is the only way I was able to fix this error. These steps were found on the Microsoft Windows Forum.

In my case, only one account was configured (obiously with admin rights) and the only way out was to press the F8 key while the system boots and start windows in ‘Safe Mode’. Then I proceeded with step 2 and beyond.

1. Log into an admin account (using safe mode if necessary)

2. Launch Regedit, go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList

3. The relevant profile existed in two forms: one with a long number, the other with the same long number plus .bak

4. Rename the one without the .bak extension to have a .old extension (or anything else really)

5. Rename the one with the .bak extension to _not_ have the .bak extension

6. In the one without the .bak extension (as changed in step 5), change refcount to 0

7. In the same profile, change state to 0

8. Close regedit, reboot

This is an example of how the registry entry looks after the fix: