I remember how much better XP64 ran with the Zero 4 mixer before the constant slog of actually trying to get it to work with Windows 7 64, so I thought I might as well aim for that in the meantime since I was all out of ideas and options for the moment. However it seems my mixer no longer works with XP64 at all despite having done so a couple of years ago. A shame really as the M6400 has full XP64 support too. The epic fail kind of panned out like this...

First snag...

It seems firewire streaming between the mixer and computer doesn't appear to work despite the 64-bit Korg Zeor4 drivers originally being specifically written for the XP-64 kernel. It seems to be stuck in a constant state of "streaming error" despite it saying that the device is working under device manager. However it produces no sound. Maybe updates for the OS might fix this?

Ideally I'd only install the one or two updates/patches needed to fix the firewire streaming problems instead of installing an entire service pack in order to keep the OS as light as possible. Generally there'll be a whole bunch of stuff in the service pack that are unessential to running an installed host OS instance that doesn't require network connectivity for its core application in purpose. 

However there doesn't seem to be any specific information on the particular updates/patches that would resolve the issue. 

Second snag...

This particular build of XP64 doesn't seem to have a working version of Windows update. Trying to use the online update features just returns a whole bunch of error codes. Possibly downloading service pack 2 and installing that will fix it.

update : 

Service pack 2 installed without any problems. Installing service pack2 for XP64 hasn't resolved the issue with firewire streaming. However it did fix the windows update feature.

After installing all the latest updates from Windows update - Did it fix the firewire streaming issue? Nope. I'm out of ideas.

Why am I so persistent in trying to get this rig working under XP 64 instead of Windows 7 64?

When Using Xp64 instead of Windows 7 64 on a TX2000z tablet a while back it worked without any firewire streaming problems at all whilst reducing the amount of audio stutter and drops. I can't figure out why this particular rig is having these kinds of problems with firewire streaming between the mixer and the puter especially because it has a faster built in firewire port and better specs in general. There's also the slight fact that I had actually made it work on this machine with XP64 a couple of years ago.

I can only conclude that it actually might be something on the mixer that has changed that is causing the problem and is stopping it from streaming. Trying the mixer with a different firewire express card on the same machine gleaned the exact same results of a streaming error.