SQL Server has a habit of popping up here and there without you necessarily knowing about it. This is a testament to its versatility and how it will generally just keep on going often without support from the IT team.
However in age of auditors, risk management and compliance, you do really need to know where these database are for a number of reasons
So how can you find these SQL Servers? These most economical solution is the Microsoft Assessment and Planning Tool which is a) free and b) simple to use. Version 5 of this invaluable tool is in beta and can be downloaded from Connect here. (You will need a Live ID).
Of course there are other Microsoft based databases (aka Access and Excel) that you need to find for the same reason. The good news is that there is another tool for this is the Office Migration Planning Manager (OMPM), which is also a free download. Having found these what should you do about them?
Essentially they need to be accorded the same processes and protection as for any other databases (I am using the term database here in the loosest sense), as these could contain sensitive or personal data that is vital to your business.
So use the free tools and understand where your key data is before you suffer an attack of the auditors!