Mach3 Problems problems problems.

[ECCO]

Preying on peoples knowledge and kindness.
The mill is set up in metric units. Lack of knowledge and understanding determined this choice, it may have been better to have chosen imperial setup units but with metric ballscrews metric was the choice. Whilst running a small program with G20 in the first line the program executes moves that are wildly incorrect. A move of Z0.100" makes the Z axis move continually in the + direction until physically stopped by operating cycle stop. After lots of messing about a G21 was inserted in the second line of the program. It worked perfectly and accurately in Imperial moves. Absolutely no idea why!!!
Next problem is trying to setup soft limits. Now completely confused. Homed the system in Machine co-ordinates onto 3 limit switches and the system zeroed X Y & Z. Measured overall possible movements in X Y & Z in mm's. Entered these dimensions into homing and limits as positive distances in X & Y and a negative distance in Z. Whilst moving about manually with Soft Limits activated get a fault message "Soft Limits < Max Min". When executing the afore mentioned program again with Soft Limits activated the error message states " Machine out of Soft Limits for Soft Limit Activation". Are soft limits based on machine co-ordinates or component datums? If its component datum would they have to be adjusted to each different component manufactured?
Next, have subscribed to Artsoft Wizards on my "House" computer, they set and simulate well. Now need to transfer this permission to the "Workshop CNC" computer, how is this achieved? Is it just a file move from "House" to " Workshop CNC" computer, in which case which file or files?
Many thanks for any help received.