Here are the security requirements that I often use for creating a Windows share for the Guest account (without a password):

Remove generic password restrictions

Control Panel > Administrative Tools > Local Security Policy > Account Policies
1.  Password Policy
   a. Minimum password age = 0
   b. Minimum password length = 0
   c. Password must meet complexity requirements = Disabled

Remove Guest restrictions for User Rights Assignment and Security Options

Control Panel > Administrative Tools > Local Security Policy > Local Policies
1. User Rights Assignment
   a. Deny Logon Locally (Remove Guest) – check this….don’t think this is required.
   b. Deny access to this computer from the network (Remove Guest)
2. Security Options
   a. Accounts: Guest account status = Enabled

Remove Guest password

Control Panel > User Accounts (Windows 7 – Click on the Manage other account link)
1. Click on Guest and remove the password (Windows 7 – you may not need to perform this step)

Note: Please be aware that this will allow anyone access to your Guest share, so be careful about the sharing permissions you set for the Guest user.