I revisited this hint recently. This script should be compatible with Tiger and higher system versions. It tries to make tandem windows from bottom of the screen up from the first two eligible Finder windows. If only one eligible window is available, it uses that one and creates another, and if no eligible windows are available, it creates and arranges two. It doesn't respect Spaces, so if a single eligible window exists, the existing window and the new window may end up in different spaces.
Here is the modified script. You can save it to ~/Library/Scripts/Applications/Finder to make it available from the AppleScript menu. You may need to create the Finder folder.
set danswer to (do shell script "/usr/sbin/system_profiler SPDisplaysDataType | grep Resolution")
set monitor_width to (word 2 of danswer) div 1
set monitor_height to (word 4 of danswer) div 1
set hit1 to false
set hit2 to false
tell application "Finder"
activate
set window_count to the count of windows
repeat with i from 1 to window_count
try
if not hit1 then
set the current view of window i to column view
set the bounds of window i to {0, ((monitor_height * 0.33) div 1 - 23), monitor_width, (monitor_height * 0.66) div 1 - 23}
set hit1 to true
if not hit2 then
set the current view of onenewwin to column view
set the bounds of onenewwin to {0, (monitor_height * 0.66) div 1, monitor_width, monitor_height}
set hit2 to true
exit repeat
end if
else
set the current view of window i to column view
set the bounds of window i to {0, (monitor_height * 0.66) div 1, monitor_width, monitor_height}
set hit2 to true
exit repeat
end if
end try
end repeat
if hit1 and hit2 then
else if hit1 then
set newwin to make new Finder window
set the current view of newwin to column view
set the bounds of newwin to {0, (monitor_height * 0.66) div 1, monitor_width, monitor_height}
else if not hit1 and not hit2 then
set onehit to 2
set onenewwin to make new Finder window
set the current view of onenewwin to column view
set the bounds of onenewwin to {0, ((monitor_height * 0.33) div 1 - 23), monitor_width, (monitor_height * 0.66) div 1 - 23}
set twonewwin to make new Finder window
set the current view of twonewwin to column view
set the bounds of twonewwin to {0, (monitor_height * 0.66) div 1, monitor_width, monitor_height}
end if
end tellMac OS X Hints
http://hints.macworld.com/article.php?story=20100820051308518