It is advisable to change your access password once awhile. I suggest once every three months. This is because to prevent any unauthorized access to sensitive data.
To change the Windows logon password:
1) Go to control panel
2) Click on the password icon
3) Select "other password" and click on "change other passwords" option
4) A new window pops up and you have to select on "Microsoft Networking"
5) Type in your current password and double type your new password. Changes will take effect in the next log on.
***You have to re log on to Windows using the new password***