TheRobot: I recently got into the BG series. I'm playing the originals. Enjoyed the first a lot, now I'm on the second.
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While playing BGII, I finally became annoyed by the fact that windowed mode is broken. Cursor scrolling doesn't work right. Borderless window was obviously not a thing (while many programs can technically fix that, I found them to be janky with BGII). Instead of just playing fullscreen and moving on, I went to work on a fix. After extensive Googling and some modifications, this AHK script was formed!
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FEATURES:
1. Allow mouse movement in any of the outer eight zones to be assigned to the keyboard (in this case, the outer Numpad keys). This means you essentially get mouse edge scrolling to pan the camera.
2. Lock cursor to game window.
3. Set game window to borderless, center it, and hide the taskbar. OPTIONAL: Change monitor resolution to match that of game window.
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NEWEST VERSION: dl.dropboxusercontent.com/s/fswo5kferjxqnwa/Mouse-to-Numpad-Plus-1.01.ahk
OLD: dl.dropboxusercontent.com/s/cdo5vl8t9inw1oa/Mouse-to-Numpad-Plus-1.0.ahk
NOTE: By default, this is set for Baldur's Gate II running windowed at 1024x768.
It can be modified for any resolution via the two "IMPORTANT" sections. Edit the script and you'll see what I mean.
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BASIC INSTRUCTIONS:
1. Run the script.
2. With your window selected, press the End key (by default) to toggle Centered Borderless Window (Note: Make sure you press the End key again before exiting the game.)
3. Press the Middle Mouse Button (by default) to toggle the Mouse to Numpad feature and Cursor Lock.
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I doubt many will have a need for this but I couldn't find anything else online so I wanted to share. If you're someone like me that enjoys playing the original BGII at 1024x768 and wants it to be fully functional in a borderless window, this is for you.

SIDENOTE: I don't know enough about AHK to do this myself but this script (with a smaller deadzone) could in theory be modified to allow middle mouse button camera panning! It's definitely possible. If I knew how to do it, I would. If anyone's smart enough to figure it out, please let me know!