Your setup is the minimum resolution to run Windows 8, but not the minimum resolution to run applications side-by-side (snapped). This is by design and I doubt there is a way around it, other than to increase your screen resolution to the minimum specs.
The following quote is from an MS development blog:
Minimum resolution and snap
The resolution that supports all the features of Windows 8, including
multitasking with snap, is 1366x768. We chose this resolution as it
has enough horizontal pixels to fit the 320px width of a snapped app,
next to a main app with a 1024px width. The specs of the Samsung
tablet that we unveiled at the //build/ conference are 11.6-inches
with a 1366x768 resolution (the Samsung Series 7 tablet in market
today). These specs are the minimum screen resolution that supports
all the features of Windows 8 on a useful physical size.