I already setup Samba on Ubuntu Server. It's working fine, but I would like to have it accessed by any user using their username and password, in any windows PC that a user would choose to use. Please help me how to do that. Is that possible? Any help will be appreciated.
Samba has a built in user authentication mechanism. You can give users permission to access your shares and use
smbpasswd to set their passwords. You can also synchronize user's login password with Samba password. Samba Server Configuration tool can help you on this, as illustrated here.
When you set up password for users, they'll be automatically required to enter it to access your shares from any computer that can access your Samba server. If your point is accessing with the same passwords they use on clients then you either need to set same passwords on clients and server, or you need a centralized authentication mechanism based on LDAP, Kerberos, etc.