Seems there is not a metric xml for the Tormach due to support reasons and I see why that is so, there is however a way to force a G21 on every reset, it is as follows.
In C:\PCNC3\Macros\PCNC-M3 there is a macro M990.m1s
You need to edit the text in the macro similar to the lines shown in bold (ie delete the Rem from the front of G21 and put Rem in front of G20)
' This macro iimplements PCNC INIT actions
' Add G21/G20 change if neededÂ
' Uses UserLabel 2, UserDRO 1209
Rem Code "G20"Â ' uncomment this to force G20 every Reset
  Code "G21" ' uncomment this to force G21 every Reset Metric = GetUserDRO (1209)
If Metric <> 0 Then
SetUserLabel 2, "millimeters"
It is probably best to make a copy of the macro to your desktop (or wherever you wish) before you edit it just in case it goes wrong
There is also a Yahoo group that John pointed me to for Tormach, here is the link
http://groups.yahoo.com/group/tormach1100/Hood