Removing strong password policy in Windows 2008
Please keep in mind that this post was written more than 2 years ago and might be outdated.
You can use gpedit.msc to change the password policy, also you can change the domain policy if you are a member of a domain to change it that way as well.
You can run gpedit.msc by doing the following.
click on the start menu, click run, type in gpedit.msc then press Enter.
Locate the “Local Computer policy / Computer Configuration / Windows Settings / Security settings / Password Policy
Change the keys you wish to change according to your existing password policies in your work place.
source: http://www.experts-exchange.com/Microsoft/Development/MS-SQL-Server/SQL-Server-2005/Q_23612846.html