What percentage of PC's run 64-bit OS versus 32-bit OS?

I'm esepcially interested in PC used in the Factory Automation market
for machine controllers and process control applications.

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Clarification of Question by stevecruickshank-ga on 06 Oct 2006 06:35 PDT

I would also like to know the trend over the next two years, such as

What is the share of 64-bit OS now?
What will it be 12 months from now? 
.... 24 months from now?

"http://news.com.com/Who+wants+or+needs+64+bits/2100-1006_3-6045931.html"
was a big help:

A very SMALL percentage of home users' and business' computers are
64-bit simply because "Most desktops and notebooks... can't even be
upgraded to take full advantage of 64-bit computing."

"I don't have usage statistics, but I expect they're pretty minimal,"
While some distributions of Linux, too, support 64-bit computing, the
market share is small in comparison with giant Microsoft.

Those users that do have 64-bit computing do so mainly because they
want to "store data in more than 4GB of memory".

The trend for the next two years:
"When Vista hits, consumers will begin to see some 64-bit benefits,
even if their applications remain 32-bit..."

Hope this helps!