Windows 7 immediately disconnects a USB drive

I am having a problem with Windows 7 x64 consistently disconnecting one specific USB mass storage drive immediately after it is connected. The drive in question is a Cowon C2 digital music player which works both in MSC (mass storage controller) or MTP (Media Transfer Protocol) modes, i.e. there are no device-specific drivers needed/available. The basic issue is the same in both MSC and MTP modes.

When I connect the player, Windows plays the "USB connect" sound and the device appears (under its correct name) in the device manager, but it never appears as a drive. The player itself displays "USB Connected" for a split-second before reporting that it has been disconnected again. Since the player, by design, reboots after it has been disconnected, Windows plays the "USB disconnect" sound before restarting the whole cycle once the player has powered back on.

I am connecting the player through an Intel X79 Chipset motherboard (Gigabyte GA-X79-UD3) to Windows 7 Pro 64-bit. The player used to work fine the first time I connected it in MSC mode, showing up as an external drive; the issue only appears when subsequently connecting it again. This can be reproduced: uninstalling the standard Windows mass storage driver (USBSTOR.SYS) from the device manager while the device is visible there, then reconnecting the device, the driver is automatically reinstalled and the device remains visible. After disconnecting and reconnecting it, the problem occurs once more. In MTP mode, driver installation fails in the first place, but that might be due to other reasons. The problem is the same: as soon as the device is connected to the computer, Windows disconnects it again.

It is not a problem with the player, since the issue does not occur on another system running the exact same operating system. It is also not a problem with the USB controller, since the issue is the same on both the Intel USB 2.0 and the Fresco Logic FL1009 USB 3.0 controller ports. I have also not had the problem with any other drive so far.

Among the things I have tried so far:

• Disabling USB legacy mode in BIOS


• Disabling energy-saving power down for all USB controllers in Windows' device manager


• Removing and reinstalling USB controller drivers


• Restoring the player to factory defaults

None of these made a difference. I would be very grateful for any hints on what else to try.

Edit: Here is another new hint; I found out that when I connect the drive before booting Windows, it is available in Windows Explorer as it should, and does not automatically disconnect. If I remove and reconnect it though, the infinite connect/disconnect-loop starts anew.