Thousands of users may have fallen victim to the hoax Windows message which was doing the rounds earlier this week, urging them to delete the sulfnbk executable.

Anti-virus vendors claim they have been deluged by users who mistakenly deleted the file, and have issued guidelines on restoring it.

The advice given to users is that they need the installation CD handy for whatever flavour of Windows they have installed. The methodology for the restoration differs between versions of Windows.

In Windows 98 and ME, users need to click Start, then Run. In ME, type 'msconfig' and hit OK; in 98, type 'sfc' and hit OK. Then click on Extract Files, and the 'Extract one file from installation disk' box appears.

Type 'c:\windows\command\sulfnbk.exe' and hit Start. When the Restore From box appears, browse to the Windows installation CD and hit OK.

For Windows 95 installations, users should follow this method. Open the Find Files or Folders box from the Start menu, select the CD drive with the Windows installation disc in it, and search for 'precopy1'.

Note down the location path of precopy1, and bring up a DOS prompt from the Start menu. Then type in the following command:

extract (location of precopy1.cab) sulfnbk.exe /L c:\windows\command

Hey presto, the file is restored.