xorg - How to get second display to work alongside primary display?

I've almost got this problem solved... I've got both displays working now. The secondary display is displaying a purple background. Unfortunately, I can't use it. (I can't move the mouse into it, etc.)

Here is the output of xrandr --verbose --screen 1:

Screen 1: minimum 320 x 200, current 800 x 480, maximum 800 x 480
LILLIPUT USB Mo connected (normal)
 Identifier: 0x175
 Timestamp:  271103
 Subpixel:   horizontal rgb
 Clones:
 CRTC:       0
 CRTCs:      0
 Transform:  1.000000 0.000000 0.000000
             0.000000 1.000000 0.000000
             0.000000 0.000000 1.000000
            filter:
 EDID:
  00ffffffffffff0031900120eb030000
  2013010380101778ca54548f54599726
  cb545400000001010101010101010101
  010101010101540b208030e02d102830
  7304000000000018000000fd00374118
  2905000a202020202020000000fc0055
  5342204d6f6e69746f720a0a00000010
  00000000000000000000000000000028
  800x480 (0x176)   29.0MHz -HSync -VSync +preferred
        h: width   800 start  840 end  888 total  928 skew    0 clock   31.2KHz
        v: height  480 start  503 end  506 total  525           clock   59.5Hz

---

And here is my xorg.conf file:

# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings:  version 1.0  (buildd@yellow)  Fri Apr  9 11:51:21 UTC 2010
# nvidia-xconfig: X configuration file generated by nvidia-xconfig
# nvidia-xconfig:  version 1.0  (buildmeister@builder58)  Fri Mar 12 02:12:40 PST 2010
Section "ServerLayout"
    Identifier     "Layout0"
    Screen      1  "DisplayLinkScreen" RightOf "Screen0"
    Screen      0  "Screen0" 0 0
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"
    Option         "Xinerama" "0"
EndSection
Section "Files"
EndSection
Section "InputDevice"
    # generated from default
    Identifier     "Mouse0"
    Driver         "mouse"
    Option         "Protocol" "auto"
    Option         "Device" "/dev/psaux"
    Option         "Emulate3Buttons" "no"
    Option         "ZAxisMapping" "4 5"
EndSection
Section "InputDevice"
    # generated from default
    Identifier     "Keyboard0"
    Driver         "kbd"
EndSection
Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "LPL"
    HorizSync       30.0 - 75.0
    VertRefresh     60.0
    Option         "DPMS"
EndSection
Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce 8400M GS"
    BusID          "PCI:1:0:0"
    Screen          0
EndSection
Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "TwinView" "0"
    Option         "metamodes" "DFP: nvidia-auto-select +0+0"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection
#################################################
############### DisplayLink Stuff ###############
Section "Device"
    Identifier      "DisplayLinkDevice"
    driver          "displaylink"
    Option  "fbdev" "/dev/fb0"
EndSection
Section "Monitor"
    Identifier      "DisplayLinkMonitor"
EndSection
Section "Screen"
    Identifier      "DisplayLinkScreen"
    Device          "DisplayLinkDevice"
    Monitor         "DisplayLinkMonitor"
    DefaultDepth    16
    SubSection "Display"
        Depth   16
        Modes   "800×480"
    EndSubSection
EndSection

---

Update: After adding...

Xinerama "1"

...I now have the secondary screen mirroring the primary one. But I'm hoping I can have separate displays.

I fixed it. The problem is that in order to use Xinerama, both displays must be using the same bit depth. (16 bits)