Make sure your game is closed before doing that.
Go in this folder %localappdata%\Plutonium\storage\iw5\players.
Then open config_mp.cfg with the notepad to edit it.
Find r_displayMode and change it to be like this (you can use ctrl+f to search for it):
seta r_displayMode "windowed (no border)"

Xerxes thanks for the help👍 , much appreciated

Thank you so much

IIRIC it is because IW5 does a lot of things which don't have to be there on its main thread.
Some already got axed by us. Non the less the your PC should reach 200 fps and you don't really want to play cod on anything higher.

It worked thanks!

FutureRave So that's what you meant. Thanks for the kind explanation!

Looking at it from a different angle, we can see the error message says you have a ult.gsc file which is referencing a function that does not exist. if you wrote this script, ask for help in the modding section because you messed up something.
If you did not create this script, content the mod creator because they may have messed up something or the script is just out of date and needs updating.
Also, do all the things Resxt told you to do.

No. You can backup the 18409 in %localappdata%\Plutonium\storage\demonware

https://plutonium.pw/docs/unlockall-max-rank/#iw5

Xerxes I can try that. Will report back to see what happens. Thanks for the tip.

That means you didn't select a folder that contains the mw3 game files.

Resxt Thank you! 🙂

That's a MW3 error, get the basegame files from here :-

https://plutonium.pw/docs/install/#iw5-modern-warfare-3

Regarding rest of the games, you need to download them through Steam, we don't condone piracy anymore.

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Xerxes okay, thanks! 🙂

FFA in killhouse custom map works back then but when i try the map again, i pretty much cant play it