D: is usually CD drive, are you positive D: is your hard drive?
I have never played Darkest Day, but when installing mods it is best to follow this order:
Baldurs Gate 2 (and ToB if you have it)
Baldurs Gate 2 official patch (or ToB patch instead if you have that installed)
Baldurdash Fixpack
Weidu Mods
Any other mods.
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