I open scrivener and another program (browser or notepad). When I give in the toolbar to ‘show windows side by side’, scrivener is maximized when the other program adopts the size for ‘windows side by side’. Both windows should be divided on screen, but this is not so.
I wasn’t able to reproduce this, testing on Windows 7. Right-clicking on the task bar with two widows open and choosing the “Show windows side by side” option correctly placed Scrivener on half the screen with the other window beside it; this worked also for tiling three or four windows and for stacking and cascading the windows. What happens if you try using Snap to drag the Scrivener window to the left or right of the screen, or use the Windows Key+LeftArrow to snap it in place that way? Does that properly size it?
You might also just try rebooting and giving it a try again, in case it’s just some gremlin coming into the system from having been running a while.