I can not unlock my ipod

Unlock an iPod Model A1199
Although the second generation iPod Nano (also known as 2G) uses a four-digit pass code that prevents unauthorized access to your iPod by locking the screen, you can also unlock the device by plugging it into your computer's USB 2.0 port.
When the 2G iPod Nano is connected to the computer it is synchronized, and automatically unlocks the screen according to the official Apple site.
In order to successfully unlock the Nano it must be plugged into the primary computer used for synchronizing content.

Click "Start," "All Programs" and "iTunes" on your PC's desktop, or click "iTunes" on the Macintosh's desktop dock.
Plug the iPod Nano's cable into the docking port on the iPod Nano.
Plug the other end into the USB port on the computer to open iTunes.
Click "Controls" at the top of the iTunes' menu, and select "Eject iPod."
The iPod Nano's screen will be unlocked once it is ejected from your computer.

Manual Guide download
http://manuals.info.apple.com/en_US/iPod_nano_2nd_Gen_Features_Guide.pdf
Unlock an iPod Nano Code
With the latest iPod Nano model, you can set a four-digit code and lock all intruders from accessing your iPod.
In order to use the device's functions again, you need to enter the correct code.
However, if you happen to lose or forget the code, you will need to find another way to unlock your iPod Nano.

Plug the iPod USB cable into the bottom of your iPod Nano.
Plug the other end of the USB cable into a free USB port on your Mac or PC computer.
Open the iTunes program by using the Dock on a Mac or the Start menu on a PC.
Select your iPod Nano from the "Devices" list in the main iTunes window.
Click on the "Sync" button to make a connection between your computer and your iPod Nano.
Click on the "Eject" symbol once the syncing process is complete.
Remove your iPod Nano from the USB cable.
The iPod's lock code will now be reset and you will be able to access all features again.
Navigate to the "Screen Lock" option in the iPod menu to lock your iPod's screen again.
Since your iPod's lock code was just reset, you will be prompted to select a new four-digit code.


iPod Support
http://www.apple.com/support/ipod/

Plug the iPod USB cable into the bottom of the iPod Nano.

Plug the other end of the iPod USB cable into a free USB port on a Mac or PC computer.

Open the iTunes application by clicking on the Dock icon on a Mac or using the Start menu on a PC.

Click on the name of your iPod Nano under the "Devices" list in the iTunes window.

Click on the "Sync" button to establish a connection between your iPod and the computer.

Click on the eject symbol next to your iPod's name after the syncing process has finished.

Unplug your iPod Nano. The device will be unlocked and you will be able to access all normal features again.


WARNING
To unlock your iPod Nano, you must connect the device to the computer it has been previously synced with.

When you lock an iPod nano that is not connected to a computer, you must enter a combination to unlock and use it. ... . You can unlock your iPod nano in two ways ... Connect iPod nano to the primary computer you use it with, and iPod nano automatically unlocks . Note: If you try these solutions and you still can’t unlock iPod nano , you can restore iPod nano.

First, make sure the hold switch on the top of the Nano wasn't activated. If not, then:
You can unlock the iPod nano screen in two ways:
A Enter the combination on iPod nano by using the Click Wheel to select the numbers
and pressing the Center button to confirm them. If you enter the wrong
combination, it flashes red. Try again.
A Connect iPod nano to the primary computer you use it with, and iPod nano
automatically unlocks.
Note: If you try these methods and you still can’t unlock iPod nano, you can restore
iPod nano. See “Updating and Restoring iPod nano Software” on page 50.

You can unlock your iPod nano in two ways:
A Enter the combination on iPod nano by using the Click Wheel to select the numbers
and pressing the Center button to confirm them. If you enter the wrong
combination, it flashes red. Try again.
A Connect iPod nano to the primary computer you use it with, and iPod nano
automatically unlocks.
Note: If you try these solutions and you still can’t unlock iPod nano, you can restore
iPod nano. See “Updating and Restoring iPod Software” on page 50 for more
information.

You can unlock your iPod nano in two ways:
A Enter the combination on iPod nano by using the Click Wheel to select the numbers
and pressing the Center button to confirm them. If you enter the wrong
combination, it flashes red. Try again.
A Connect iPod nano to the primary computer you use it with, and iPod nano
automatically unlocks.
Note: If you try these solutions and you still can’t unlock iPod nano, you can restore
iPod nano. See “Updating and Restoring iPod Software” on page 50 for more
information.

You can unlock your iPod nano in two ways:
A Enter the combination on iPod nano by using the Click Wheel to select the numbers
and pressing the Center button to confirm them. If you enter the wrong
combination, it flashes red. Try again.
A Connect iPod nano to the primary computer you use it with, and iPod nano
automatically unlocks.
Note: If you try these solutions and you still can’t unlock iPod nano, you can restore
iPod nano. See “Updating and Restoring iPod Software” on page 50 for more
information.

You can unlock your iPod nano in two ways:
â Enter the combination on iPod nano by using the Click Wheel to select the numbers
and pressing the Center button to confirm them. If you enter the wrong
combination, it flashes red. Try again.
â Connect iPod nano to the primary computer you use it with, and iPod nano
automatically unlocks.
Note: If you try these solutions and you still can’t unlock iPod nano, you can restore
iPod nano. See “Updating and Restoring iPod Software” on page 50 for more
information.

You can unlock your iPod nano in two ways:
â Enter the combination on iPod nano by using the Click Wheel to select the numbers
and pressing the Center button to confirm them. If you enter the wrong
combination, it flashes red. Try again.
â Connect iPod nano to the primary computer you use it with, and iPod nano
automatically unlocks.
Note: If you try these solutions and you still can’t unlock iPod nano, you can restore
iPod nano. See “Updating and Restoring iPod Software” on page 50 for more
information.

You can unlock your iPod nano in two ways:
â Enter the combination on iPod nano by using the Click Wheel to select the numbers
and pressing the Center button to confirm them. If you enter the wrong
combination, it flashes red. Try again.
â Connect iPod nano to the primary computer you use it with, and iPod nano
automatically unlocks.
Note: If you try these solutions and you still can’t unlock iPod nano, you can restore
iPod nano. See “Updating and Restoring iPod Software” on page 50 for more
information.