Huge lag whenever certain spells effects happen like the death spell's or finger of death.

I think this is because I am on a laptop and it's loading the scripts from a file on the slower hard drive. Every. Time.

So every instance, for example, of the death spell being triggered results in a separate load.

So if you kill 10 people, that's 10x the lag.

And there is also a lag when grabbing and when placing any item. So every time I need to move an item in my inventory, it looks for the sound file for item placement/selection on the disk.

Any ideas? I did a search before posting this and found one or two similar unanswered issues.

I have tried disabling hardware acceleration and using windowed mode. I have set the game to administrator mode. Still happens.

Yup. I had this problem back when I was using Intel HD 3000.

It does (i7 6700 HQ), but I am using the Nvidia card. Actually, I have tried both cards. Still happens.

The reason I think it's the hdd is that I hear it start up whenever the problem happens AND because it happens with both sounds (moving inventory items, selecting characters) and spell effects.

Now it may not be the HDD, because I just tried copy/pasting the installation to my SSD and it still did it. Then again, a copy paste might still be referencing the old install, so I will try a full reinstall to the SSD, even though I don't want to as it has little room left as it is. 16gb of ram, dude. And I don't run much in the background and have a pretty clean system. That's not it.

Have you tried adding the game to your anti-virus ignore/excluded list?

yep. one of the first things I tried. forgot to mention it. I set the exe, the folder and the documents folder with the save games etc to ignore in windows defender. I don't have any other antivirus.

Oh :( Sorry that was all I had as a solution. Hope you get it sorted soon.

Considering I've had this problem for over a year now, it's not likely. But I haven't tried the SSD, so I will let you know.
edit: Nope. Still happens. Fresh install and latest patch.

"""Enhanced""" Edition indeed.

Well, it seems your system is quite a lot better than my own pc but the only problem I run into is a CTD when I ALT+Tab in BG1EE

The only thing I can think of is maybe an issue with power saving mode.

Are you certain that every file has been excluded?
Unless you need to be online at the time, I would close out the AV and try playing with it off; that should either eliminate the AV or identify it as the culprit. (Antivirus software is a resource hog even under optimal conditions, and these Infinity Engine games constantly load procedures, which are small executable code script files, triggering the AV.)