Different image size

I use MapPoint 2004 on two different machines and I automate it with VB.Net to do some map actions and save the map like this:

oMap.SaveAs(myImapgePathAndFileName, MapPoint.GeoSaveFormat.geoFormatHTMLMap, False)

:roll:
But the result is different in resolution size of the created image_map.gif.

First machine is Win2K Server with a display resolution of 1024x768.
The size of the image_map.gif is 564x380px.

Second machine is Win2K Prof with a display resolution of 1600x1200.
The size of the image_map.gif is 888x725px.

Is there any way to get influence on the resolution of the saved image file?

Thanks in advance.

Alex