[17.5] Windows has *how* many sound channels??

One, nominally. In fact, most PC sound cards will provide more than this but (or so I'm told) Windows itself only provides one as its baseline, and Director doesn't actually talk to the hardware directly. This is not so much of a problem as it may seem, since DfW incorporates Macromedia's MacroMix DLL which enables the mixing of multiple simultaneous sounds at differing volumes and (with 4.0.4) sample rates prior to output via the single channel.

There are still two problems. One, mentioned above, is that this may introduce a noticeable delay in your sound playback, so it may not run in sync with the visuals (or rather, you'll have to resync it for each platform). I think this is caused by MacroMix, but I don't know for sure.

The second problem is that there's still really only the one sound channel, and while Director has it no-one else can. In particular, QuickTime for Windows can't have it, which means that either your QuickTime movie can play its soundtrack, or your Director movie can, but not both at the same time. (I feel certain there must be a workaround for this, but if so nobody's told me.)

Also, note that the number of sound channels for which Director allocates buffers depends on the settings in your DIRECTOR.INI (or PROJNAME.INI) file. I think this specifies 4 sound channels by default (though again, I don't have a copy to hand), but this can be increased up to 8. So, if you want to use more than 4 channels, make sure to edit your .INI file accordingly.