Unless you turn off the (automatically on) option that says "overwrite archive on updates" then you will only always have one arcive from the most recent update. (that is to say only if you turn on (the automatically off) option that says to archive before update)
To uninstall entrenchment completely (in order to only install SOASE) you have to manually delete folders and manually edit your registry. There are more specfic instructions in other threads dealing with compleatly uninstalling entrenchement.
my SOASE archive is 793,xxx KB in size, my entrenchment archive is 96,xxxKB in size. I have 5 total archives none of which will unarchive on a fresh install of XP.