When you perform a search for a file in Windows XP. The default setting is for XP to ONLY return files in the "Search Results" pane - when they are registered file types to a program on your PC.

In other words if you are looking for a file that is NOT registered with an application on your PC, it will not be found using the default search settings.

However, you can turn off the default by a quick Tweak of the registry!

Open the Registry editor (type regedit from the Run command) and navigate to:

HKEY LOCAL MACHINE\ SYSTEM\ CurrentControlSet\ Control\

ContentIndex

Double-Click the value named:

FilterFilesWithUnknownExtensions

..and change the value from 0 to 1

Exit the registry editor and reboot!