I have the same problem, when I use KVRT in Windows 10 PE, I get a message that I can't read the C:, I have used the -d parameter to specify the X drive, but it still says: can't load the driver
I found that KVRT creates a sys file in C: when I use it in full Windows, so I hope you can provide the ability to change the location of the sys file creation via command line, so that might be helpful to solve this problem.