You dislike the new Aero Snap feature. Here's a My Digital Life tutorial on turning it off. Or an alternative registry hack (same source)
Aero Snap is definitely a welcoming
feature to many users who need to
quickly maximize or half-maximize
windows for viewing or comparison.
However, some Windows 7 users may have
different need or usage behavior, such
as those need always drag a window to
the edge of the desktop to work on
other tasks, or just need to monitor
and look at the some tiny corner part
of the window. In Windows 7 system
with multiple monitors, Aero Snap auto
adjustment of window may go erroneous
too, where the maximized window may
span across multiple monitors, making
it harder to read.
Use the trick below to disable and turn off Aero Snap ability to auto arrange or auto maximize window when dragging.
- Go to Control Panel.
- Click on Ease of Access link or Ease of Access Center icon.
- Select Change how your mouse works or Make the mouse easier to use option.
Tick the check box for Prevent Windows from being automatically arranged when moved to the edge of the screen with the mouse under “Make it easier to manage windows” section.

Click OK or Apply to make the change effective.
Once Aero Snap is disabled, the window won’t be automatically maximized and arranged when window is dragged to the edge of the screen, including both top and sides of the screen.