1. Click Start, click Run, type C:\windows\repair, and then click OK.
2. Right-click the Autoexec.nt file, and then click Copy.
3. Click Start, click Run, type %windir%\system32, and then click OK.
4. In the System32 folder, press Ctrl + V to paste the Autoexec.nt file in this folder.
Should work its off microsofts support page.