visual c++ - winusb_initialize returns false -

i use zte usb modem device. device installed ports class (driver usbser.sys). followed msdn example "how access usb device using winusb functions". fine until call function winusb_initialize.it returns false getlasterror 87 i-e error_invalid parameter.i found solution on "http://www.microchip.com/forums/m653017-print.aspx" doesn't help.when try change winusb.inf file in x86 folder,computer says access denied though have logged in administrator. kindly me.

thanks in advance

i handle need is:

   bool bresult;    winusb_interface_handle usbhandle;    bresult = winusb_initialize(devicehandle, &usbhandle); 

if bresult true, means initialized winusb correctly.