Hello Fia -
I'm using Word 2007 now...
It is not possible to select more than one picture at the same time if Text
Wrapping is set to In-Line with Text, i.e. if the picture is part of the
line of text with chars before and/or after.
It is possible to select more than one if Text Wrapping is set to anything
else (e.g. Square, Behind Text, Through etc., i.e if they are part of the
page or paragraph and thus have an Anchor mark to allow them to move
independently of the text.
Once selected go for Picture Tools/Format picture and Size then set the
common height and width that you want. If they were originally all set to
Lock Aspect, this will be maintained and only one of height or width is
possible.
I'm sure word 97-2003 would work v similarly, if not the same.
Hope this helps
Good luck - Mike