Vista - Can't get right document sizes

I've tried asking this question before, but I apparently wasn't clear. So let
me try again: I'm scanning a small document, about 8 inches wide by about 4
inches deep. When I try to print it out in Microsoft Office Picture Manager,
or any other app for that matter, it always comes out huge, running off the
paper, even after I have "resized" it. I've been at this for over a week, and
I just can't seem to get it right. I'm using an HP photosmart 3180, with
Vista. I'm about ready to take a hammer to this whole system and get a Mac
(my friends have them, and never have the problems that Windows computers
seem to have). I never had these problems with Win98 and a slow old computer.
What can I do to get these scans to come out right.

Chet