Windows 8.1 does allow you to skip the Microsoft account sign in, but they do not make it obvious. If you have used it to login, then for the sake of networking, use a local account :
http://www.techrepublic.com/blog/wi...-tip-change-to-a-local-account-in-windows-81/
The other thing you may want to do is make it behave more like windows 7:
http://www.pcworld.com/article/2043243/how-to-boot-to-desktop-mode-in-windows-8-1.html
When using windows and attempting to access a NAS using SAMBA, it will attempt to login using your existing credentials. As mentioned in this thread, you can create an account on the NAS that matches your windows login and password, then give the NAS user access to the folders you want using the NAS web interface.
Alternatively, you can map a network drive and check the box: "Connect using different credentials". If you use your NAS web login information, the drive will map and you'll have full access. This, btw, is not great practice in terms of security, but it will get you started.
Better practice is to create several users on the NAS (none with admin access) that mirror your windows users' login information, and give these users just the access that they need to the NAS folders. That way when an encrypting virus or similar shows up, it would not have access to everything.
On some NAS's you can also enable guest user access to each shared folder (using NAS web interface) and leave it at that. This method may introduce longer delays and cause browser issues..so I don't use it.
Windows 8.1 btw has some magic under the hood with respect to windows SMB3 multichannel that I'll be writing about in the blog series. If you're interested in fast network performance, SMB3 found in windows 8 and server 2012 is essential. After upgrading half of my team to windows 8.1 the one comment that they had: "it's faster" and "it feels snappier". No hardware was changed, and six workstations were updated.