Origin Version (Select Help-->About Origin): 7.5 Operating System: XP
this is not a scientific question or problem. this is more a formatting issue. when i export a graph as a png- or tif-file there is always a relively large (white) space between the x-axis and the lower border/edge of the image. this is problematic when arranging these images with a subtitle (in a scientific paper for example), because of the relatively large distance between the x-axis/axis-label and the subtitle describing the image. i spent days on this but found no way to downsize the sourrounding white border. apparently, this was not a problem in origin 6.1 but i do not want to downgrade.
Open the Tools->Options dialog and click on Page tab. Then change the Margin Control dro-down to Tight or Border. It is probably set to Page which exports the entire page and thus includes the white space that you want to leave out.