I recently backed up my iPod to a folder on my external, and when I go to search for a certain song in the folder it shows up with "no results" when I know it is clearly in there.

I have tried the indexing thing or whatever, and maybe I messed something up? Not sure, but it is really bothering me. I have spent the whole day trying to figure this out.
If you're doing a
regular Search of the "Indexed locations" for your external HDD files, you won't find them in the Indexed locations unless/until you ADD those files and location to your Indexed locations setting, and/or have the device plugged in when you're searching.
Another way to approach the problem, is to do an
Advanced Search of the NON-indexed locations. In Locations, select either: Everywhere or Computer, and be sure to check: "Include non-indexed, system and hidden files." The search will definitely be slower than a non-Advanced Search, but it
will search your entire system and assumedly, locate your external HDD files - again, if you've added them and/or have the device plugged in.