You don't need to download any driver in order to root your Lava Iris n501 device. If the phone is not recognized by your PC when you're trying to root it, press Windows + Pause/Break key combination and open Device Manager. Expand the Universal Serial Bus controllers list, right-click the driver and select Uninstall. After that, reboot your PC, connect the device using the USB cable and press Scan for hardware changes icon from Device Manager. Windows should automatically find and install the driver.
If you still have issues, you can try rooting the device using SRSRoot. All you need to do is to download the software from the official web page, to connect the phone to your PC, to enable USB Debugging and Unknown Source options and to check Root All Methods.