Searching for *.zip will find any files that you have compressed using XP's
built-in ZIP file creator/extractor ("compressed folders").
However, to my knowledge there is no way to run a search to find all files
that are currently compressed using the NTFS compression. However, you can
use Folder Options in Control Panel to "show encrypted or compressed ntfs
files in color" (see the View tab). This option will cause compressed files'
names to appear in blue font, and encrypted files to appear in green.
SK