How to check the status of SQL Server?
You'd have more options here:


Perfmon (or ResourceMonitor on W7+) for general resource information;
Activity Monitor in Management Studio;
Inside SQL Server:


Glenn Berry's DMV queries;
Adam Machanic's stored procedure sp_WhoIsActive.



There are also many other external monitoring tools (some free, some paid) that you can use, but these ones are free and worth mentioning as a first step in your work.