So I tried all this and it works! Thanks! One problem remains, however... The window locks the mouse cursor so I can't do anything outside the game, and on the occasions that it does work outside the game (usually only when I first start it) I still can't use the mouse to move the window. It just gives focus back to Arcanum and then the mouse doesn't work outside the game.

Well, it's about three years probably, but in case you still need a workaround for this, after you Alt+TAB out of the game and are back at your desktop press CTRL+SHIFT and you should get control over your mouse again.

You are a wonderful person, my friend.

I'm trying to run Arcanum on my window 10 computer, and I faced the usual lag issues and fixed them all with the info on this forum. But now I have another issue. My mouse buttons don't work (both). The cursor moves fine, no trouble. The buttons that don't seem to work. I tried the full screen version and the windowed version, but the problem remains. When I run the game without all the changes to stop the lag, the buttons worked fine.