While checking out old posts, I came across this one in which I was having the same problem. My Insignia MP3 player would slow down to a crawl transferring files when in USB mode. I like to copy my MP3 files the old fashion way without any additional software but the standard file system did not recognize the drive when it was in "Portable Media Device Mode" wanting to use "Media Transfer Protocal".
I came across this fix and wa lah! everything is coming up roses.
09.29.2008 at 08:25AM PDT, ID: 22597349
I don't believe this question was answered, so here is the solution:
Right click "My Computer", select properties -> Hardware -> Device Manager. You will see something in the nature of "Portable Media Device" listed in the device tree. Double click or right click your corresponding item. Select Driver -> Update Driver -> Install from List -> Don't Search -> Show compatible hardware. In the selection options should be "USB Mass Storage Device" (The inf file for this is usbstor.inf). This method will install your MP3 player with a drive letter, and skip the preconfigured Windows Media assignments...
Hope this helps someone else.