ITunes Transfer - Songs Missing???

OK here's the situation.
Desktop PC- Open iTunes, it shows 17,868 songs; look at preferences and find the folder where music is stored. Go to that folder and copy it to an external HD. Hook external HD to my Mac NBP. Open iTunes. Find the folder I have set up for my iTunes music. Go to that folder and place all of my music there. iTunes now says I have 15,752 songs. What gives? 18k songs is a LOT of music to manually scroll through to compare to see what is missing and where it went. I have repeated this process a couple of times with the same results. Somebody please talk me away from the window ledge...I am about to jump!
Thanks all-
Jeff

Enable the Homesharing feature in iTunes 9. It's built just for this.

Thanks Bob. Do I have to delete everything in my iTunes folder before transfering through Home Sharing to prevent a gazillion duplicates?

Got it figured out. Selected "Show items not in my library". There are my 2,000+ songs. Drug them to my library...TA-DA!!! Wish I had asked earlier. Many, many thanks.
Jeff