So the scenario:

We have  Cisco/NICE software working in conjucntion to handle calls thru our call center. One feature is Silent Monitor where the supervisor can listen in to live agent calls as they happen.

So we get some errors when trying, Cisco thinks it may be our NICs. All our nics are intel pro/1000 GT, these of course are not certified with Cisco.
The reason is intel nics turn off vlan tagging, Cisco needs this.
So theres a registry fix - http://www.intel.com/support/network/sb/CS-005897.htm.

Ive done the registry tweak.

How can I see if vlan tagging is working without logging into the cisco software? Is wireshark an option and what do I look for?

thanx in advance
 

Yes, with a packet capture tool you should be able to capture some packets and see if the is a 32bit field (vlan tag) added to the packet.  

I use Wireshark on Intels had hadn't noticed a specific problem, perhaps winpcap (which drives the monitor mode on the card) adjusts. I can see tags fine.

So I suppose I'm saying even if wireshark works it may not prove anything. There are some tools that rely on the stack which have basic monitoring (IPTOOLS, ANALOG-X Packet capture) which may be a better test but you'll have to do more work dissecting the frame by hand to establish if tags are there.