I came across this thread while attempting to install the Quad flash microSD card zif pata on my Cowon X7 (link here:
https://www.amazon.com/gp/product/B07538C6PX/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1). I used this adapter to partition it and format it to FAT32 before connecting it to the COWON (link here:
https://www.amazon.com/gp/product/B07FW9WC1F/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1).
The COWON can see that it is there in the disk usage widget (with an exaggerated bar)) but is not detected by the player software to choose music. Also, the new X7 HDD does not show up as a USB drive when connected. The firmware version installed is 2.14.
I matched the geometry of the partition to match the original start at sector 63 instead of 2048 with the same drive size as the original and matched the disk label to X7_HDD. When I use the built-in format function of the X7, it generally just fouls up the disk and loses the entire partition requiring me to create it again with the computer. It would seem that this Quad Flash will not work with the X7 (at least not with my limited disk skills) - I'll just use it for my iPod classic (which it is proven to work for). Preferably, I will figure out a way to use it in the X7.