When you search for a file in Windows Windows searches only for file types it recognizes. Files that aren't listed in the 'Registered file types' list are ignored. Fortunately, a simple edit of the Registry will make Windows search for every file, regardless of its extension. Open the Registry Editor as described above, and then navigate to and select:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\ContentIndex. Double-click the FilterFilesWithUnknownExtensions icon in the right pane, change the 0 in the 'Value data' box to 1, and press Enter.
To ensure that Windows XP searches for every possible file, select All Files and Folders under 'Type of file' in the Search Companion pane. (If you don't see this option, click More Advanced Options.) Check Search system folders, Search hidden files and folders, and Search subfolders (as desired). In Windows 2000, click Search.
Options, check Type, and make sure that (All Files and Folders) is selected in the resulting drop-down menu. Check Advanced Options, and make sure Search Subfolders is checked. Finally, to ensure that Windows 2000 finds system and hidden files, choose Tools, Folder Options and click the View tab. In the 'Advanced settings'list, select Show hidden files and folders. Uncheck Hide protected operating system files (Recommended), click Yes to acknowledge the warning, and finish by clicking OK.
" Windows XP Tips: Find Every File "
Reference : techpraveen.com