tell application "Finder"
activate
if not (exists Finder window "thisone") then
make new Finder window
set target of Finder window 1 to folder "thisone" of disk
"drive1"
end if
end tell
Of course this check is crude - it would match any window called
'thisone", so if you're using a common folder name this test might
not be sufficient, but you can add whatever check you're
comfortable with.
I suppose one way of approaching that issue might be to address the
folder itself:
tell application "Finder" to tell folder "thisone" of disk ¬
"drive1" to if not (exists container window) then open
