Have you searched the forums?

if all fails. Wait for the next version which is due in a few days.
maybe -s

The installation batch files have big problems if you try to install in DOSBox. I was able to modify the install.bat file (to replace any reference to WHAT.EXE) for KQ6 and it installed fine.

i can play this game (installed), no problems.
perhaps you can try to download a installed version.

Or manually copy all files to a specific folder like C:\KQ5

With the King's Quest Collection, which I believe is what you are referring to as the '15th Anniversary Edition', if you cd into the specific directories for the game on the CD itself, you can use the game's own installer, rather than the selector batch from the collection CD to install each game.

Well i dunno what else to add.
I have the old i guess original but it came in a cd case off a shelf version of King's Quest 5 CdRom voice/sfx version. from 1992.

It ran fine for me.

I guess if you have the collection use the original installers in the respective King's Quest game directories and I suppose it will work fine.

I have KQ 6 but it's a rerelase from Slash corp. I have a lot of Slash corp rereleases. They're working on an Adlib bug to fix some soundblaster/adlib sound issues in a number of Sierra Games.