What is "Northwind"
The Northwind Database
is a sample database provided by Microsoft, based on a fictitious company called Northwind Traders. I think there are two or three versions of it. The earliest version had/has a problem with the "Order Form" in that you could accidentally switch an order from one customer to another. I demonstrate how to fix this problem in this blog here.
The Samples may not be Suitable for Production
I have noticed one or two problems in other Microsoft Access sample databases, so I would be careful before putting any of them into a production environment, make sure you test them thoroughly and have them checked over by someone who knows a bit about the foibles of Microsoft Access.
Mix & Match is Unnecessarily Difficult
The other thing that seems careless to me regarding the Microsoft samples is that one sample with a customer table and another sample would have a similar customer table but they were not exactly the same! There are slight differences, extra fields, things like that. This might seem a minor irritation however, it means that you cannot easily combine one sample with another. Let's say you had a vehicle tracking database and you wanted to add the facility to invoice by linking/combining it with another sample, you are not able to mix and match components from the various samples, not easily anyway!
I don't know if ALL or ANY of the links provided are safe. Please use you own judgement...