How do I simply reset where iTunes looks for folders?

Question

I took all of my music from the resident iTunes folder on my laptop and put it in a folder on an external hard drive.  I added music to the external hard drive as well.  Now, my iTunes shows the titles from the old resident folder which is now empty, and the files from the correct external HD folder which I designated.  How do I reset the iTunes search criterion, so that it no longer shows the ghost files (songs) on the iTunes folder on my laptop?  I want to reset the search and start from zero.  Is the only option to highlight the entire music library screen and then delete it all, after disconnecting the external HD?  This should be a no brainer and I am sure that Apple thought of this and has a simple solution, right.....?  What am I missing??

Answer 1

Sorry that I was unclear, tt2.  My iTunes version 10+ has 2 folder locations; the one on my laptop where the iTunes software is resident and, a folder on my external hard drive.  I told iTunes to look in the external folder, so it now has 2 the locations; the resident iTunes on my laptop (default) and, the folder on my external hard drive.  I copied all the files from my resident folder in iTunes to my laptop, putting it in the external music folder (deleting all doubles).  Then I deleted all the files on my resident iTunes on my laptop.  Now, iTunes still shows the deleted files, with an exclamation mark on the left side of the music library screen on iTunes.  How do I reset iTunes so that it re reads the internal or resident iTunes folder, sees that it is empty, then I instruct iTunes to look at 1 folder on my external hard drive.  I need to reset the entire on board library/music list, to reflect only the empty iTunes folder on my laptop and, the single folder on my external hard drive.  My laptop cannot hold all the new music, so I put it all on an external hard drive (210Gb).
I can highlight & scroll down the entire music screen that shows the empty file titles from the laptop's hard drive (iTunes default location on computer), and also the correct external master file, then hit delete (after disconnecting my external hard drive, so that the actual music is not deleted), but this seems to be a bass ackwards methodology to do what should be a regular and simple feature of iTunes....