Help needed with PC/DAC

My Dell computer keeps rejecting my DAC (usb) and returning to its default factory sound outlet ("Realtek High Definition Audio"), which is definitely lower fidelity.
I have tried to find someone (here on Maui) competent to set up for me, but failed so far.
This has happened with 2 different Teac 301 DACs, so I suspect it is a computer issue.   The sounds are already downloaded on a big external hard drive (NOT livestreaming). 
Any advice appreciated.

A few of the choices you need to make are counter intuitive, so try going through this setup guide. Its for the AQ Dragonfly, but the choices you need to make should be the same.

Sorry, I thought I put the link in yesterday.

If you have any trouble, just go to AQ's website and click on the computer audio tab, then select setup guide.

may want to consider turning OS updates off.   dumps my drivers everytime and resets to the realtek card.  annoying.  
thanks paulsax, good to know I am not alone
my plan now is to duplicate all the music on the external hard drive onto a new external hard drive, and then use my spare computer to play it to the dac/preamp/amp/speakers
completely disconnected from internet
3 years later, just wanted to explain that my problem was solved by installing a $10 POWERED USB hub between computer and dac.