If you set up a user account in Windows and you want to allow the user account to have a blank password you may find it a little difficult. In order to accomplish this you probably need to change a couple settings in Windows.
The password does not meet the password policy requirements. Check the minimum password length, password complexity and password history requirements.
To allow a blank password go to Start -> Run and type in gpedit.msc then hit enter.
You should get a window that pops up and has a whole bunch of settings you may have never seen before. On the left side expand Windows Settings -> Security Settings -> Account Policies and then click on Password Policy. On the right side you will need to change a few of the settings.
The three settings you will need to change are Maximum password age, Minimum password length, and Password must meet complexity requirements. Change maximum age and maximum length both to zero and disable the complexity requirements. Once you have these three settings changed you can just close out the window and now you should be able to set a blank password for your user account.
If you cannot change these settings you may be joined to a domain which has these settings locked down. I can’t help you there, but this should help in most other cases.
Let me know if this helps, or doesn’t help, in the comments.