I had this same issue with a Cisco Catalyst 2960-C Series PoE. I was using Win 7 and a USB console cable..
I installed the driver on my HD like normal and let it extract to its default location.
I went to Start> Devices and Printers> and saw that my Cisco Serial was COM4 instead of COM1. Default in Putty was COM1.
Then I went to Start> Computer (right clicked) selected Manage> Device Manager> Ports (COM & LPT). I right clicked my Cisco Serial (COM4) and selected Update Driver Software> Browse my computer for driver software> Let me pick from a list of devices on my computer> and selected Cisco Serial. That worked. For some reason Win 7 was defaulting to a Default USB Serial Port driver instead of the needed Cisco Driver..I was able to console into my switch once I asked Win 7 to use the right driver.
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