If you are writing code, the first thing you test for your self is whether you can connect to the server. Technically even if user created databases are not present, the system databases will always be there.

Read this article I wrote on connecting to SQL Server:

http://www.codeproject.com/Articles/8157/ADO-NET-101-SQL-Connection

If you are connecting through a client such as SQL Server Management Studio then if you can bring up the SSMS Screen then go to FILE and click to connect to Object Explorer. You get a window Connect to Server and there you click on the handle to see all available connected servers.

You can find many more articles in my blogs: http://hodentek.blogspot.com