Disable "Snap Assist" and "Snap Fill"

Snap Assist

Chooses atuomatically an other app (maximised or not) which Windows believes to be the right joice to be shown next to the app you want to be halve the size of the screen

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced]
"SnapAssist"=dword:00000000

Snap Fill

Chooses automatically an other (not maximised) app which could fill the empty space and snaps the app moved to a corner or side to fill the space left by the other app. Very random and annoying when you really only want a window to be half the screen size.

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced]
"SnapFill"=dword:00000000