Another one of the tools that I have become very used to using is Process Explorer.  You can get detailed information on what exactly is going on with your system.  The display mainly consists of two windows.  The top window displays what processes are currently active.  The bottom window can run in a couple different modes.  If you are running process exporer in handle mode you well see the handles that have been opened by the processes in the top window.  You can also run process explorer in dll mode.  The bottom window will then disaplay the memory mapped files that the process in the top window have loaded.

I highly recommend that you get used to using this program.  It will give you detailed information that task manager just can not give you.  I guarantee that knowing how to use this program will separate you from just being another server administrator.

Current Version - v11.20

Process Explorer Website
http://technet.microsoft.com/en-us/sysinternals/bb896653.aspx