Why is SQL Server 2005 consuming so much memory (and it is not even running)

Solution 1:

The SQL Server IS running - whether or not you have Management Studio have open. SQL Server will use as much memory as it needs and can get - by default - you can change that, if you want to limit SQL Server to a certain amount of RAM. But be aware: SQL Server needs a good chunk of RAM to work properly - if you restrict it too much, it'll slow down considerably.

Solution 2:

SQL Server will use as much memory as it needs. You don't have to be running SSMS for it to use memory - you have things like the data cache which will cache data in memory when queried to make it faster to retrieve for subsequent calls. Any connections being made to the db server will use memory. It shouldn't be anything to worry about, if the OS needs more memory for other tasks, SQL Server can release it. But if there's no pressure for memory, then SQL Server will use as much as it can.