To configure the search to include all file types, follow the next steps:

1. Open the Registry Editor click on the Start button on your taskbar, then click on Run and type "regedit" and click on OK to start the regedit utility.
    
2. Expand HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\ContentIndex (see picture 1).
   
   

   Picture 1

3. Double-click the value "FilterFilesWithUnknownExtensions"  and set the data value to "1".
    
4. The modifications you made will be in effect after you reboot your PC.

To cause Windows XP to search for hidden and system files:

1. Click Start -> Search -> All files and folders -> More advanced options.
    
2. Check the Search system folders and the Search hidden files and folders boxes.
    

NOTE: These setting will be remembered.

NOTE: You must uncheck Hide protected operating system files in Folder Options -> View.