When you are trying to log on to Windows 7 with your account, if you receive the following error message (see below image), use the solution here to fix the issue. This solution has been proved to work for many Windows 7 users who have encountered this issue like you.
First, start Windows in Safe Mode. If you are not sure how to enter Safe Mode in Windows 7. The solution is to fix the user account profile, which requires you to modify the registry. You need to follow the steps carefully, as modifying registry incorrectly might cause serious problems. It is recommended that you back up the registry before you get started, so you can restore it if a problem occurs.
If you log on when Antivirus is scanning your PC, a user profile may get corrupt, according to Microsoft. But there must be other reasons. You may try rebooting the PC to fix it quickly. In case it doesn't work, you have to restart the system again and boot in Safe mode if it doesn't work. Press F8 before you get to the loading screen and choose Safe Mode from menu. By choosing Safe Menu, you will get into the default Windows Administrator account but some features will not work.
1) Click Start and type "regedit" on the search box and hit "Enter".
2) It will open the Registry Editor and you have to go to these keys – HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList
3) Double click "ProfileImagePath" entry after clicking each S-1-5 folder to look for the related account. Rename the folder if it has extensions like .ba or .bak by following Microsoft's detailed instructions. If not, follow the remaining steps.
4) Once corrupt profile folder is found without .bak extension, double click on "RefCount" and change the Value to 0 and click on OK.
5） Double-click "State" and get Value to 0 again and click OK.
6) Close the Registry Editor and reboot the PC. See if you could log on to your account again.