How to fix logon issue in windows ?

If you are working in an infrastructure that deals with Windows, you have probably fallen in the situation where you tried to log on the windows and have faced error like "The User Profile Service service failed the logon". That means, the default profile, which is stored at C:\Users\Default, has some incorrect permissions or is corrupted some way. In this case, Logon is not possible, if the default profile’s NTUSER.DAT file is no existing or somehow got corrupted and then simultaneously the user profile service generate an event with ID 1508 and source User Profile Service in the application event log under Event Viewer.

You might be thinking what is NTUSER.DAT ?

Well I can only say that every user profile created on a Windows operating system has an Ntuser.dat file. It is a registry file which contains register settings for individual users account cause each users profile contains personal files and preference setting like browsing history, documents folder, custom settings for desktop properties which is specific to each other


Registry (file also known as Windows registry) is nothing but "central hierarchical database" that contains information about the software, hardware and user profiles contained on a computer defined by Microsoft. Windows refers the registry files throughout its operations and NTUSER.DAT supports the configuration of "HKEY_CURRENT_USER" which is the branch of same registry file now we are talking about.

you can check the NTUSER.DAT file at C:\Users\(Your_UserName) location.

Let’s talk about Temporary File

I am sure, you will not like this type of file when you will know about it. So, basically what temporary file is? The name itself says that it will not last longer on your computer. On Windows, your logon session will need a user profile. Generally a profile already exists and our operating system will load that. Suppose if there is no profile present there, then windows will automatically create a new fresh profile from the default profile.

A default profile is nothing but a profile template that contains various settings such as desktop colors, backgrounds, icon placement, and Windows Explorer settings. You have observed many times that whenever you log on to the new system for the first time. You waited for little bit long time and meanwhile your windows were creating your new profile resulting on the screen with a texts messages saying that “Welcome, Preparing your desktop, customizing your settings etc.” and then you find your desktop screen.

Coming back to the temporary file. So either one of the processes like loading your existing profile or creating a new one from default profile fails Windows cannot log on the user unless it creates an “Ersatz” which lasts for f duration of your session. Such type of profile is knows as Temporary profile which is like your local profile but it gets deleted whenever you logoff the windows.

Simplest way to fix the issue

So, the question is how to fix this issue and somehow here I got the solution that the easiest way to fix a corrupt default profile is to delete the content of "C:\Users\Default" and copy it from a working system. We need to make sure, that the machine you are copying from has the same operating system version and language in order to avoid the occurrence of mismatching the content.

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Rohit Sharma
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Rohit Sharma

Hi There! My name is Rohit and I am working in the one of MNC as Web Apps developer. I have been in this tech industry for last 3.6 years. This blog is just a part of my career journey.
Ready to make new mistakes without repeating the previous ones.

"All life is an experiment. The more experiments you make the better"

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