I cannot transfer all of my i-tunes from my desktop PC to my laptop PC. Of about 800 tunes, it "cannot find" about 100. Where are they?

Question

My itunes are stored on my desktop. When I move them to my laptop, about 100 of 900 tunes are "not found." Thus, I cannot upload them from my laptop to my i-pad.

Answer 1

First, empty the Trash if you haven't already done so.
Use a tool such as OmniDiskSweeper (ODS) to explore your volume and find out what's taking up the space. You can delete files with it, but don't do that unless you're sure that you know what you're deleting and that all data is safely backed up. That means you have multiple backups, not just one.
Proceed further only if the problem hasn't been solved.
ODS can't see the whole filesystem when you run it just by double-clicking; it only sees files that you have permission to read. To see everything, you have to run it as root.
Back up all data now.
Install ODS in the Applications folder as usual.
Launch the Terminal application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Terminal in the icon grid.
Triple-click the line of text below to select it, then drag or copy — do not type — into the Terminal window:
sudo /Applications/OmniDiskSweeper.app/Contents/MacOS/OmniDiskSweeper
Press return. You'll be prompted for your login password, which won't be displayed when you type it. You may get a one-time warning not to screw up.
I don't recommend that you make a habit of doing this. Don't delete anything while running ODS as root. If something needs to be deleted, make sure you know what it is and how it got there, and then delete it by other, safer, means.
When you're done with ODS, quit it and also quit Terminal.