How do I edit the .ini files such that stack sizes are unlimited? Or must I achieve this in another way?
Thanks.

What you're looking for is the Baseitems.2da file. Simply changing these files will not work, however. You'll need to include your modifications into a hak pak (which must be installed in the override directory) then modify the module/campaign you want to play to use that hak pak. Maybe someone more familiar with NWN modding could give you more specifics, but this isn't something where you can just change one line in notepad.

Do you have the volume up in Sound Options?

Which Sound Provider is selected in Advanced Sound Options?

Where do I get the baseitems.2da file?
Thanks.

In your NWN folder, look for a folder called "source", it'll be in there.

My source folder is empty. However, I have a file in the nwn root folder called 2dasource.zip, which has many .2da files inside (including baseitems.2da).

What is the largest number I can put for "Stacking"?
Thanks.

I believe its 9999, but I could be wrong. My own stack sizes cap out at 1000 and thats just for ammo.

I made some changes to the baseitems.2da file and placed it in the source folder. I changed the columns "Stacking" and "ILRStackSize" for some of the items (mainly those that can stack) to 99999, but there was absolutely no difference at all when I went back into the game to try to stack my arrows and potions together beyond the default amounts.
Am I doing something wrong?

Don't put your edited baseitems.2da file into the source folder, copy it into the NWN/override folder.

ahh I see what I was doing wrongly now
Thanks!

Also, what items (which rows) in baseitems.2da describe adamantine, skeleton's knuckle, fire beetle's belly, fairy dust, dragon blood, etc? I would like to stack these items as well.

miscsmall - 1x1 size items
miscthin - 1x2 size items
miscmedium - 2x2 size items
misclarge - 2x3 size items

Thanks! It works for the crafting items!

I noticed that it doesn't work for "quest/plot items" though, but that doesn't matter as you don't need to carry more than 1 of each quest item anyway. (I tested this by repeatedly asking Nyatar for his 2 quest items, then dropping it on the ground.)

Unique and custom made items can have modified stack size, different from that in baseitems.2da, and they usually do. It can be edited in the game editor and if you want every unique item to be stackable (which is not much needed anyway, as you said), you have to modify each one of them in the editor and make a .mod file or put modified items' .erf files into Override directory.