dsetup.dll - Windows Defender won't let me add it as exclusion
 

I read the threads where people were having issues with that file being missing, and saw that it was probably a problem with my antivirus software. I found the file in the zip (it wasn't extracted), pasted it in extracted folder, tried to add it as an exception on Windows Defender. Not only would it not add, but the file itself wouldn't stay pasted in Titanium. It keeps disappearing. It lives now only in the .zip and on my clipboard.

Anyone know a way around this, please?

The same thing happened to me this morning. Funny that there was no problem when I first installed the new patch files on Sunday. Anyway, you can get round it by turning off real-time protection. Though this is something you probably dont want to leave off forever.
You can find instructions on how to do that here:
https://www.youtube.com/watch?v=_0_A9D0JeVo

Thanks Krovice - I actually just did that and got the game to start. But yeah, not a good long-term solution. Plus, it says that you can only turn it off "for a short time" before it turns back on automatically. I have no idea when it'll turn itself back on or what will happen to my game when it does.

Just fixed this issue for me on Windows 10, not sure if it's the same issue you're having.

But I first launched 'Windows Security' setting -> click ' Virus & Threat Protection' -> click 'Protection history'. From there I found a 'Threat quarantined' entry for the dsetup.dll file. I clicked the drop-down action to 'Restore' the file and everything started working again.

Another thing you can do besides turning off real-time protection is to add exceptions. I know you said you tried to add an exception to the file and it wouldnt let you, but have you tried adding an exception to the folders?

I did this by going to Windows Security. Under 'Virus & Threat protection settings', click 'Manage settings'. Then under 'Exclusions', click on 'Add or remove exclusions'. Then click Add an exclusion'. I then selected 'folder' and pointed to my Everquest folder and selected that. I then added another exclusion for the folder with the patch files.
I was then able to turn back on the real-time protection and the file stays in place.

Someone said in another post that he added an exception to the file, so Im not sure why you couldnt. But I guess we have multiple ways of accomplishing the same goal.

If you use WinEQ, you can turn off antivirus / protection / w.e for just the 10 mins to open WinEQ, then enable them again. As long as you leave WinEQ open, you can launch p99 whenever even with antivirus on

Thanks, all. After I'm finished playing today I'll try these solutions and update if one of them works. Much appreciated!

Huge find Vokrin.

Thanks.

This did it, thanks so much!