Here you will find the steps necessary to modify the Domain Security password length policy for Windows 2008 Server.
Note: The following must be executed on the Windows 2008 Server.
To modify this behavior you must launch the Administrative Tools program group and follow the steps below:
1. Open the Group Policy Management console.
2. Expand Forest: DomainName.Com
3. Expand Domains and locate your DomainName.Com leaf.
4. Right mouse click on Default Domain Policy and from the context menu select “Edit”
5. Navigate to the following: Computer Configuration > Windows Settings > Security Settings > Account Policies > Password Policy.
6. Double click on “Passwords must meet complexity requirements” and from the Security Policy Setting tab set the policy to “Disabled”
7. Select "OK" to initiate the change and close the dialog box.