If you have an XP disc (retail, oem or restore). Insert your XP disc into the CD drive and open it.
You will see a folder named i386, open it and resize the window so you are able to see the desktop.
In the folder you will find the file
autoexec.nt_; - right click on it, drag it to your desktop and select copy here.
To use WinZip to expand the file:-
Open WinZip and drag the file into the main window - choose extract - on the screen which comes up make sure "all files" is selected then in the main window above expand C: then expand WINDOWS, click on System32 to highlight the folder and finally choose extract.
The file should now be in System32 folder.
If you do not have a disc, the file can be downloaded from here -