Most (almost all) inkjet and laser printers have a required margin.  This
gives the printer an area it can use to handle the paper and in most cases
is not able to be printed in no matter what settings you use.  That is the
bad news.

Now for the good.  Some printers can.  These are usually referred to as
'full bleed' printers and can print the entire surface of the paper, from
page-edge to page-edge.  These printers are usually more expensive, but have
become slightly more common in recent years.  If your printer has this
ability, then refer to the user manual for instructions on how to set it up
to do so.

However, all is not lost if the printer can not print edge to edge.  You may
just need to supply a larger paper size and trim it down, after printing is
completed.

You may want to wander over to:
http://www.pptfaq.com/FAQ00097.htm
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http://www.pptfaq.com/FAQ00774.htm