You can reinstall the firmware. Just do it manually, there will be instructions in the post. I also recommend formatting the player first. After the firmware is reinstalled, the USB mode settings will go back to the default setting of autodetect.
Unplugging the player when it’s still transferring data is a very bad idea. It can permanently damage your firmware beyond repair and it’ll void the warranty.
One other thing, if WMP takes over the transferring of data again, if I recall correctly, there should be a “stop sync” button on the lower right corner of the display for WMP.
