The latest SDK does not have any firmware updaters:
GHI NETMF v4.2 and .NET Gadgeteer Package (04-30-2013)
There is readme that says they have moved online:
C:\Program Files (x86)\GHI Electronics\GHI Premium NETMF v4.2 SDK\Firmware Update
“Updaters have moved, they can be found on the website.”
Do you have a link?