Here is the solution to another issue I experienced after upgrading to Windows 10.
Two different serial port adapters with Prolific PL2303 chips (with VID 067B and PID 2303) did no longer work. Some googling brought up the below page which claims that the problem is counterfeit chips and new drivers trying to fight that, but I am not at all sure this is the real issue. Anyway, the solution (allegedly an old driver) offered on the page solved the problem:
The driver below only supports the Prolific-based adapters supplied by Serialio.
I am using the driver I linked to for adapters marked “ST Lab”. I do not really know if that is a real supplier or just some brand name. I doubt the driver is specific for some particular adapter manufacturer. I think it is specific to the chip used.