I grew up with this game and love to revisit it whenever I get the urge to play a good old space sim game. However, each time I had to fight with technology to get the thing running, and Windows 11 was a tough one. There are many helpful posts here with correct answers, but not everything works for each person, none of the individual solutions worked for me, but combining the solutions seemed to work.

So here is what I did:

Turn OFF Data execution prevention (DEP)
No, I don't mean add I War as an exception, I mean turn it off completely. Your PC should be fine for the time you are playing I War just don't go running any weird apps you don't trust.

To do this press the WINDOWS KEY + R and type sysdm.cpl
Click on the Advanced tab
Under performance click settings...
Click the Data Execution Prevention tab
Ensure this option is checked: "Turn on DEP for essential Windows programs and services only"

Then restart your PC

Open the folder where Iwar.exe is located

Use the nGlide config to configure it how you like, although what worked for me was:
1920 x 1080
4 : 3
60hz
Off (may cause speed issues I'm not sure)
1.0
On

Next, create a shortcut (not a copy) of IWar.exe
Right click the new shortcut and click properties
In the "Target" field, after the last quotation mark " symbol, add -b -16
Apply
In the compatibility tab, I have the program running in compatibility mode for windows XP (SP3)
and Run this program as an administrator check

That's it, you should be able to launch IWar from the new shortcut, and everything will hopefully work.
Such a pain to get a game from 1999 running in 2024 I know