How To Fix The User Profile Service failed the logon

The User Profile Service failed the logon. User profile cannot be loaded
Sometime you must have seen this problem while logging in to your windows (7 or 8) so this is not a very big issue actually so first here we will be discussing that why it happens and then will discuss about the solution.

This issue may occur if the user profile was manually deleted by using the command prompt or Windows Explorer by a user or by some program. A profile that is manually deleted does not remove the security identifier (SID) from the user profile list in the registry. Since the SID is still present, Windows will still try to load the profile by using the ProfileImagePath that points to a nonexistent path. Therefore, the profile cannot be loaded

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This solution is not written by us, just found that on Google and posted it here so that peoples can solve this error by their self.

Step By Step Guide

First please login your computer in "Safe Mode", so know about safe mode? if no then when switch on your computer then press and hold F8 button and then you will be promoted to black screen with white written on the page and there you have to select "Safe Mode" then proceed to next step.

Step 1

• Open the Start menu. In the Start Search area, type regedit and press Enter (if prompted by UAC, click Continue/Yes). In regedit, go to: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList
• Expand the ProfileList key and look for the SID key (named "S-1-5"...) with a long number that ends in ".bak". Click it, and look at the ProfileImagePath value in the right pane to verify that this is the user account profile that has the error.
• a) If you have two SID keys with the same number (with one ending in ".bak" and one showing the affected user account in the ProfileImagePath value), continue to Step 2; b) If you have just one SID key with the ProfileImagePath value showing the affected user account, proceed to Step 3.

Step 2

• Of the two SID keys that corresponds to the affected user account, right-click the SID key that does NOT end in ".bak" and click Rename.
• Add .bk to the end of the numbers and press Enter.
• Right-click the other SID key that DOES end in ".bak" and click Rename.
• Remove only .bak from the end of the numbers (so that it has the same name as the other SID key did before you renamed it) and press Enter.
• Now go back and Rename the first one with .bk to .bak now at the end of the numbers and press Enter.
• Proceed to Step 4...

Step 3

• Right-click the SID key that corresponds to the affected user account and click Rename.
• Remove only .bak from the end of the numbers, and press Enter.
• In the right pane, right-click the RefCount value (if none exists, right-click the right pane and click New and DWORD (32 bit) Value, then type RefCount and press Enter), and click Modify.
• Type 0 into the Value Data textbox and click OK.
• In the right pane, right-click the State value and click Modify.
• Type 0 into the Value Data textbox and click OK.
• Proceed to Step 4...

Step 4

Close regedit and restart the computer. You should be able to logon now...