Dual Monitor Configuration, Maximizing spreads between monitors

Question

I connected an external monitor (dell ultrasharp 18 inch) to my laptop (laptop screen 15.4 inches).

When I maximize a window in any monitor, it immediately spreads between both monitors in an uneven fashion due to the different resolutions in them.

Can I avoid the window from spreading between the two monitors? I just want to maximize in individual monitors.

Previously, when I was using Ubuntu 11.10, the monitors got automatically configured the way I wanted. But then I had not installed the propriety ATI/AMD drivers and I was running Unity 2D but now I am running unity 3D. Is this issue related to the propriety ATI/AMD drivers and Unity 3D?

I installed the prpriety ATI/AMD drivers y following this link http://ubuntuportal.com/2012/03/new-ati-catalyst-12-3-has-been-released-how-to-install-in-ubuntu-12-04-and-linux-mint-12.html

I also tried this How can I stop a window maximizing across two screens? It didn't help.

FYI, lspci output

00:00.0 Host bridge: Intel Corporation 2nd Generation Core Processor Family DRAM Controller (rev 09)
00:01.0 PCI bridge: Intel Corporation Xeon E3-1200/2nd Generation Core Processor Family PCI Express Root Port (rev 09)
00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09)
00:16.0 Communication controller: Intel Corporation 6 Series/C200 Series Chipset Family MEI Controller #1 (rev 04)
00:1a.0 USB controller: Intel Corporation 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #2 (rev 05)
00:1b.0 Audio device: Intel Corporation 6 Series/C200 Series Chipset Family High Definition Audio Controller (rev 05)
00:1c.0 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 1 (rev b5)
00:1c.1 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 2 (rev b5)
00:1c.2 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 3 (rev b5)
00:1c.3 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 4 (rev b5)
00:1d.0 USB controller: Intel Corporation 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #1 (rev 05)
00:1f.0 ISA bridge: Intel Corporation HM65 Express Chipset Family LPC Controller (rev 05)
00:1f.2 SATA controller: Intel Corporation 6 Series/C200 Series Chipset Family 6 port SATA AHCI Controller (rev 05)
00:1f.3 SMBus: Intel Corporation 6 Series/C200 Series Chipset Family SMBus Controller (rev 05)
01:00.0 VGA compatible controller: Advanced Micro Devices [AMD] nee ATI Seymour [Radeon HD 6400M Series]
07:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 06)
0d:00.0 Network controller: Intel Corporation Centrino Wireless-N 1000
13:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTS5116 PCI Express Card Reader (rev 01)
19:00.0 USB controller: NEC Corporation uPD720200 USB 3.0 Host Controller (rev 04)

fglrxinfo output

display: :0.0  screen: 0
OpenGL vendor string: Advanced Micro Devices, Inc.
OpenGL renderer string: AMD Radeon HD 6400M Series
OpenGL version string: 4.2.11566 Compatibility Profile Context

Any help would be great. Thanks

Answer 1

I switched to unity 2D and my monitors work the way I wanted in my question.

Both my monitors behave like 2 independent screens (Not like one Giant desktop). Dragging a window from one monitor to other automatically resizes the window to fit the resolution.