Launch iTunes, go to Preferences: Advanced: iTunes Music Folder Location
move it to your new drive.
You may have to re-import your music (meaning: After you drag and drop all your music over to the new drive, you may need to have iTunes scan for new music, you will not need to re-rip or re-buy music as long as you don't delete anything)
Change the preference
move the music to the new location
rename my old itunes music folder to something else (not delete, just rename the top folder)
iTunes will still show my old library, but I won't be able to play anything
I will delete my itunes music from itunes (not from windows) (view all, select all, hit the delete key) making sure to choose the do not remove from my HD option.
I will then drag my new iTunes music folder into the iTunes library folder, it will re-scan and add in my entire library from the new drive.
Since this is your first time doing this, I'd back up everything just in case.
Glockers of the Old Dominion #101