Slow Windows USB device detection after many (200+) unique individual connections
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I have a windows utility which flashes firmware to a device utilizing an FTDI usb chip. I plug a device in, the utility detects it, the utility does its job, I unplug the device and a new device is plugged in, repeat.

That works well, however, once 200 or 300 or so devices have been connected on a single machine, Windows doesn't want to detect them right away anymore. When I plug a device in, it sometimes takes 5-10 minutes before I hear the "bing" sound of device connection. Additionally, windows reports that it failed to install the device drivers. Despite that report, the utility can detect the device and talk to it just fine after that.

I have flushed pretty much everything that seems relevant from:

 * HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\USB\
 * HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\FTDIBUS\
 * HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\DeviceClasses
 * HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\ 

but the device detection is still slow. The slow detection persists across reboots.

What other stuff should I investigate, to restore the device detection to be near instant, as it is before connecting so many devices? Are there files hanging around in the window directory that I should modify or delete?

Thanks