No. When you install the 2018 Band-in-a-Box you're asked where RealTracks and RealDrums reside. Once you tell BiaB they are located on the external drive then BiaB will quit using the RealTracks and RealDrums located on your primary drive.

One issue you might encounter though is Windows may change the drive letter if you plug the drive into different USB ports or plug a USB memory stick into a port prior to plugging in the USB drive. You can avoid the drive letter issue by going to control center and manually assigning a drive letter to the external USB drive.
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Jim Fogle
2018 BiaB (512) UltraPlusPak RB 2018 (Build 5)
Sonar Home Studio - Cakewalk Music Creator 6 - Audacity
i3 laptop, 64bit Win 7, 8 GB ram, 480GB HDD
Music at: http://fogle622.wix.com/fogle622-audio-home