It sounds as if you still have a password policy in place on either an OU or your Domain. Let's focus on removing the policy for now and then you can address the policy and its' settings later.
Find out how many policies you have.
Open up MMC,and add the "Group policy" add-in.
Once you select the group policy add-in and select "add" you will be presented with a box to select which policy you want to review. Select the "browse" button and then select the tab "All".
This will allow you to look at all of your policies.
TIP: you can add each of your policies into the MMC from this window so that you can check them all at once.
Select "OK" and then "finish" to add each policy.
Once you have your policies within the console, maximize the MMC window, expand a policy, then expand "Computer Configuration", expand "Security Settings", expand "Account policies", highlight "Password Policies" to see your settings in the right pane.
To turn your password policy off, make sure your Password Policies are set to "Not Defined".
Write down which policy it is you modify for future reference.
There is another way to manipulate your policies with group and user permissions, but this can be a cumbersome task. The aforementioned steps will also expose you to all of your policies and also identify ones that may not be needed.
Good Luck.