It would be an odd move in terms of the market though? ie how many windows machines/networks are there which are hooked up to PLCs (well, there are a lot, but many orders of magnitude less than consumer uses of windows and pcs).

Having said that - it could be VERY lucrative for them - just not in volume. Very much high end expensive product sales (which may be a direction they want to go in - now that MS and others are rolling out built in virus protection with the OS?).