First you can download the intstaller for rpiboot for Windows from github at HERE
Then I always prefer Debian which can be found HERE
I’m using the DF Robot Router Board from HERE
Huge shoutout and thanks to Jeff Geerling for the board.
To get the CM4 into rpiboot mode you have to switch the little switch on the DF Robot Board labeled
Now you have to install the program, then open up rpiboot and let it do it’s thing then it’ll be mounted