locate which is a standard tool on GNU/Linux. Of course,
locate has Windows ports, so it should work out-of-the-box on Windows too if
locate is installed..
See also: LocateFilesAnywhere
This is developed on GnuEmacs but should work on XEmacs, too.
To use this on MacOS?, you can use the mdfind command instead of locate.
"mdfind" (list "-onlyin" (getenv "HOME") (concat "kMDItemDisplayName == '" input "'wc"))