How to Fix a Winlogon.exe Application Error
1. Press 'Start' and then 'Run.' Type SFC.EXE/SCANNOW to run the System File Checker. Click 'Enter.' System File Checker is included in all modern versions of Windows, such as XP, Vista and Windows 7.
2. Insert the Windows installation CD if requested. The System File Checker will begin the process of transferring or replacing any missing files, onto your computer. Restart your computer after the process is complete.

3. Enter safe mode by pressing 'F8' immediately upon restarting. Safe mode starts your computer while only loading the programs and drivers required to run your operating system.
4. Turn on your virus protection program, and run a complete scan on your computer. If you do not have a form of virus protection on your computer, install one before continuing. Most Internet providers offer a free version of antivirus software to their customers. If your provider does not offer a free version, purchase a copy at your local retail store or download a free or trial version.
5. Reboot your computer normally. If these steps do not solve the Winlogon.exe application error, repair your system from the Windows installation CD (see next section).
Repair Your Computer System
6. Insert the Windows Installation CD and reboot your computer.
7. Click 'Enter' when prompted, to enter Windows Installation Setup.
8. Press 'F8' when prompted, to accept the terms.
9. Use the keyboard to select the current version of Windows, and press 'R.' Your computer will begin the process of repairing your system. After the process is complete, your computer will reboot and allow you to continue normal use.