Options > Don't use HTML paragraph auto spacing

The way paragraph spacing works was changed in Word 2007.
In Word 2003 the paragraph line spacing before and after could be changed from the Paragraph dialog box.
If you had two paragraphs of text the space between those paragraphs would be the sum of the "after spacing" from the first paragraph and the "before spacing" from the second paragraph.
Select File > New to create a new default document
Add two paragraphs of text
Apply the following line spacing to the first paragraph
SS - 0, 10
Apply the following line spacing to the second paragraph
SS - 15, 0
The total line spacing between the two paragraphs was 25 points.

In Word 2007 the default paragraph line spacing before and after behaves slightly differently
If you have two paragraphs of text the space between them is not the sum of the after and before but is the larger instead.
Select File > New to create a new default document
Add two paragraphs of text
Apply the following line spacing to the first paragraph
SS - 0, 10
Apply the following line spacing to the second paragraph
SS - 15, 0
The total line spacing between the two paragraphs is 15 points.