I mistakenly bought an X5, thinking it was an X5D. Is there a software upgrade or even a hardware fix that might give it the 'D' qualities? If not, I'll happily keep it - good board either way.

Jeepers! When I saw the headline I thought you were talking Hammond X5 - sorry to still be in the stone-age :-). Okay, I'll even admit to still owning one - been trying to sell it for years.

Seems I also misunderstood the title and expected to see pictures of a BMW X5.
Duh!!!!!

I've already replied to your question over at the General Discussion forum but here goes:

In short: No. There are no software/hardware upgrades that will turn your X5 into X5D. There is a ROM upgrade that doesn't do much. There also was (rumoured and unverified) some odd type of mod that allowed for AKAI load.

But nothing that doubles the polyphony or adds the missing 2 or so megs of ROM multisamples.

On a sad note I just lost one of my old Korgs. Took it to a repair shop this morning but I'm not too optimistic. At some point I even considered selling the thing but kept it as I just couldn't let go.

Oh, those old synths...