Download Process Monitor from MS. It will show all process, registry,
and disk activity in real time.
http://technet.microsoft.com/en-us/sysinternals/bb896645.aspx
That might be too much information.
A simpler place to start is
Run Task manager (C-A-Del Task Manager, or right click on taskbar and
select from menu)
Go to the performance tab
Under Physical memory I would expect Cached to be 2000-3000, and free less
than 100
Under Kernel I would expect Total to be well under 500
Under System I would expect page file to be about 2000M
Press Resource Monitor
Look at the graph for memory - the scale should 100 Hard Faults/sec, and
you shouldn't see much green graph.
Look at the graph for disk - the scale should usually be 100KB/Sec, and
the blue line should rarely be visable.
Click on the disk section and the first line should have a response time
well under 100ms.
If this is so then it is routind background activity that isn't impacting
you - its only disadvantage is it prevents the disk spinning down because
it is never idle.
The disk detail will list what process is accessing what files. If the
image is svchost then look up the PID in the services tab of Task Manager
(you may need to check show processess from all users in the Process tab)
I am basing this on my system which only has 2GB of RAM and guessing how
the extra 2GB alters things.