(Use microsoft pbrush.exe found in windows folder)
When printing with Mircosoft Paint 
Goto FILE/PAGE SETUP
set size to A4
set left margin to 20 mm
set top margin to 20 mm set others to 0 mm

Then Goto FILE/PRINT
click PROPERTIES under SETUP check BEST button
paper size to A4
and print...

From Russ-TV!