Problem:  

NLB does not balance ICMP by default.  

Solution: 

NLB works great with ICMP (after a simple registry change):

HKEY_LOCAL_MACHINE
   \System
      \CurrentControlSet
         \services
            \WLBS
               \Parameters
                  \Interface
                     \{GUID}
                        \FilterICMP

Change the value from 0 to 1.  NLB will balance ping requests like a champ!

Backgroud:  

Conventional wisdom holds that Microsoft Network Load Balancer (NLB)only works with TCP and UDP traffic. Indeed, ICMP requests return replies from multiple sources by default.  

Backgroud:

Obscure URL on Technet has an interesting tid-bit:  http://technet.microsoft.com/en-us/library/cc709622(v=ws.10).aspx

Apparently Windows System Image Manger can enable ICMP load balancing "ICMPFilteringEnabled" -but only for new installations.

What about our existing load??

I sent the URL to talented programmer and sys-admin, SAK, who quickly found the necessary registry attribute.