I agree- that was kind of nice.
On the multiple instances of AC issue, simply this:
Windows doesn't actually default to the "last installation of ArchiCAD" -that isn't quite correct. Windows defaults to the last association of the file name to whatever program has the latest registry creation date (that CAN be changed by the way). This is especially true when the extension ID (in our case, something like *.pln, or say, *.dwg) is the same across various version of the same *.exe and application to access them!
The biggest problem is unless you do some registry editing, you're stuck using just whatever VERSION of AC is associated with the file association in windows. So while you CAN edit the install method and change the dates of the association, whatever you do you're pretty much stuck with unless you're REALLY savy with registry editing!
(check the HKEY_CLASSES_ROOT for this list and editing, but back up your registry BEFORE you do squat! =
http://winbeginners.com/graphics/hkey_classes.htm )
so if you have AC7, AC9, AC 11 and AC 12 installed, and you edit the registry to have the plans open under AC9, then AC9 will be the one it opens with from now on, until you re-edit the registry. I just tried it out so I can confirm this.
So the "convenience" of simply clicking a file and having to do some SERIOUS registry editing to perhaps have windows associate *,pln files based on creation date (LOL- now we're getting crazy) with differeny versions of AC, vs. simply dragging the file over the short cut (either on desktop, quicklaunch or a custom tool bar you make) is ...well. You can drag or you can launch AC first like D' says, or sit down for 6 months and learn how to customize your registry and try and do stuff the windows crew has struggled with for the last 10 years to get right (LOL!)....
If you ONLY want to open ALL your files from now on with an OLDER version of AC, you either have to uninstall the newer ones, or change the date in your bios when you install the apps in windows so that the one you WANT to be the default, if the one that the bios was set to latest... Capice? So some juggling with your computers settings, which might give you windows licensing errors or Graphisoft errors, but really is a LOT of trouble for avoiding the work-around.
IF you're still curious why Graphisoft hasn't "fixed" this (least on a windows platform) I don't think it CAN be fixed. IT is a windows issue- windows associates *.*** (in our case, *.pln, for instance) with an app and that's that. Windows as it stands currently does not have a simple default smart-sensor to associate file creation programs with the prospective file names when the file name extension is the same as files created with a later version of the same program or file extension. The reason for that is it would create a NIGHTMARE of code and registry problems in half of microsoft's products- something they are already out on a limb with in the windows registry (the most fragile and vulnerable part of their operating system!).... renaming the various versions of AC (archicad.exe) won't solve this, as windows itself can not differentate, without 3rd part applications, the association of file extensions based on creation and date with different applications.
NOW that would be cool though, eh? Maybe it can be done, and I would think a smart coder could write something we could use, but it is going to be WAY out there on a wing in left field, with maybe a few hundred users in the world at best- which leaves problems that are created by it for your OS, totally in no-mans land and without support.... so maybe it already has been done and disappeared because of this.
Good luck regardless.
oh- the other solution for Graphisoft is proprietary extension names- which creates more spider web problems in the registry and solves less than it creates- AND such a function would render sharing the files between versions of AC and different workstations a major nightmare for the licensing at the very least. A music software maker from Germany tried this and it pretty much put them out of business by version 4- none of their file formats were compatible or had problems with earlier file formats, rendering upgrades a total waste of time and killing off their customer base. Graphisoft is right to leave this in microsoft's no-man's land and stick to simply letting the latest version be the default.
p.s.
we've taken to naming the files with a 2nd extension to indicate the version created with or last edited with so that we don't run into opening issues... I.E.
08412E01.09.pln
year,
project number, Existing/Remodel,
Version.
AC-version*.pln
Date and version is more important for sorting, so I've got the AC variant stuck at the end. Put the AC version where it makes sense for your sorting method. Usually we only have a few files per project, as they're organized in company folders that are the same for every project.