This is truly old testament stuff…. Ok, enough with the Ghostbusters….

If you’ve ever had to support multiple Office environments, you’ve probably already discovered the sheer joy and wonderment that is VMWare.

But, if you have to develop against them, sometimes, it’s awfully nice to have the Office version you need right there on your main box.

It’s not terribly common knowledge, but you can actually install various versions of Office side by side (with the sole exception of Outlook, which only tolerates a single version on a machine, for dark and unholy reasons).

However, if you’ve tried, you’ve most likely snagged yourself on a rather irritating burr.

You start Word 2000, say, and you get an MSI (Windows Installer) prompt saying it’s got to repair something. You click OK, and let it do it’s thing. But then, later, when you start Word 2007, you get a similar prompt, this time for the newer version. Back in Word 2000, same prompt again. Grrr.

There’s a few KB articles out there about this annoyance, but nothing that really resolves it completely satisfactorily.

After some experimenting, however, it looks like it is possible to make various Office versions coexist more or less peacefully, without bashing each other over the head with a virtual tire iron every time one or the other fires up.

The key is registration, esp with Word. Each time it starts, Word checks certain registry entries to make sure they point to that version of Word. If not, you get that “repairing” prompt and the long delay while Word resets everything.

This is great for Joe User who accidentally scrambled his registry and just needs Word to work right again, but it sucks for Pauline Power User who has 3 versions of Office on her machine, and switches back and forth between them constantly.

The trick is to prevent Word from reregistering itself when it starts.

Details of how to do just that are in one KB article on the Microsoft site, but they only go so far as to detail how to do this for Word 2007.

The problem is, what if you want DOC files to normally open with Word 2007, but still have Word 2000 on the “Open With” list via the right click menu? I’d imagine this is a pretty typical scenario.

Take the following REG script, save it to a REG file, and dbl click it to merge it into your registry (it shouldn’t require any special privileges because it only deals with the user hive).

Basically, creating the NoReReg value for each version of Word will prevent the reregistration from happening when you start Word.

Windows Registry Editor Version 5.00

;This will keep Word 2007 from reregistering itself each time you run it
[HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Word\Options]
"NoReReg"=dword:00000001

;The same trick works for Word 2000
[HKEY_CURRENT_USER\Software\Microsoft\Office\9.0\Word\Options]
"NoReReg"=dword:00000001

;for Word xp
[HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\Word\Options]
"NoReReg"=dword:00000001

;and for Word 2003
[HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Word\Options]
"NoReReg"=dword:00000001

Be sure to have run the version of Word you want to use actively as the LAST THING YOU DO before running this script; ie, if you really want Word 2000 to be the default editor for DOC files, run it, let it register itself fully, and THEN run this script.

Of course, setting the NoRegReg value back to 0 (via REGEDIT) will revert things back to the way they were and allow that specific version of Word to reregister itself.

Furthermore, the newer versions of Word support a “repair” option on the HELP menu that will perform the reregistration as well.

One note; the Word 2000 and 2007 versions I’ve tested explicitly. The XP and 2003 versions I haven’t checked explicitly yet, so YMMV. However, I was utterly surprised that this trick (which was documented for 2007), actually worked with Word 2000.

And finally, neither Excel nor Powerpoint appear to need any of these shenanigans, hence their MIA status in the above script.