libusb docs indicate that -3 is:

http://libusb.sourceforge.net/api-1.0.16/group__misc.html#ggab2323aa0f04bc22038e7e1740b2f29efa131f3c2f6f2bb40bc6fb60ccb6f3152f

LIBUSB_ERROR_ACCESS Access denied (insufficient permissions)

Sounds like you have a permission problem?  Best I can do to help you, I've never even seen a windows machine. :)

-Michel

On Wed, Oct 30, 2013 at 12:14 PM, Jonathan Rawlinson <m0zjo@qsl.net> wrote:
>
> Hello all
>
> I am trying to get the python wrapper "pyrtlsdr" working on Windows, it works fine on Linux
>
> The dongle works fine in SDR-SHARP.exe
> It imports correctly but prints the following error when I try to initialize the Dongle:
>
> Traceback (most recent call last):
> File "C:\Users\M0ZJO\Desktop\RA_Astro\FFTPrint Test.py", line 4, in <module>
> sdr = RtlSdr()
> File "build\bdist.win32\egg\rtlsdr\rtlsdr.py", line 60, in __init__
> % (result, device_index))
> IOError: Error code -3 when opening SDR (device index = 0)
>
> RTL_FM also returns the same error.
> Can anyone help? I would be very grateful!
>
> Many thanks
>
> Jonathan/M0ZJO