1. Put your Windows CD/DVD into your DVD drive.
2. Click your 'Start' menu, click 'All Programs,' click 'Accessories' and click 'Run.'

3. Type 'expand D:\i386\logonui.ex_ %windir%\system32\logonui.exe' without the quote marks. Replace 'D' with your CD/DVD drive. This replaces the corrupt LogonUI application with a fresh one from your operating system's installation resource.
4. Restart your computer and remove the disc from your drive.