hi,,,, first off the info you asked for,,,,,,,,,
threads are,,,,,,,
http://en.wikipedia.org/wiki/Thread_%28computer_science%29What is audiodg.exe?
http://www.neuber.com/taskmanager/process/audiodg.exe.htmlnothing to worry about,,,,
the blue lines in the RAM window in Resorce monitor represent the hard fault levels,,,, also known as the page file,,, when things are being swapped from hard drive to the ram,,, if your pc is doing a hell of a lot of this then this could indicate that you need more ram as the page file is continuously running out of temporory storage in the ram and is swapping out all the time with the harddrive,,,, at the moment mine has a blue line about a 3rd of the way up from the bottom,,, this represents that of my 3gb of ram only 30% of it is being used,,, the more i use the higher the line moves up,,, but to do this i have to put the pc under serious load,,,
in R/M at the bottom there is a bar named "learn more" expand this and click on the offerings for more info on R/M, you can also learn more on this tool by clicking help tab at the top of the window.
reading the rest of your post,,, this is all normal behaviour for a pc,,, when your streaming the cpu usage will go up as there are a good few processes at work here,,, its a bit more than just downloading a file to the desktop,,, if your running a few tasks then the multi core technology will come into play here and allocate tasks to cores,, so you will sometimes see one core with more usage than another,,, if your doing one task then it will allocate all resources to this and cpu usage will be lower as its spread across cores,,,, unfortunately i dont see the kind of figures your getting as i use a quad and dont run with multi tasks going all the time,,,,
as for the hard disc activity this is all normal aswell,,,, when your doing something there will be lots of activity as the page file is swapping things between the ram and superfetch is also kicking in,,, things your doing are saving to the hdd,,, and even when your finished and the pc is in idle, then the hdd comes out to play again as things are set to run when the pc is idle,,, like indexing,,, i have mine set to index the full C: drive,, then the auto defragger will kick in also, things like avast anti virus will start to check files added etc,,, updates will be looked for on a lot of programs as most of these things are set to update when pc is idle,,,, if your worried about things running that you dont know aout,, or that nasties are in the machine then here are a couple of good tools to play with,,,,,
security wise,,,, download MBAM free version and SAS free versions,,,, update and run once a week,,, i have MBAM full version which is set to update at 6pm every night then run a scan at 8pm nightly,,, this is not needed but if the resources are there and the pc does not slow then why not,,,,,,,,
also i would download a program called win patrol
http://www.malwarebytes.org/mbam.phpand how to use it
http://www.udel.edu/topics/spyware/malwarebytes.htmland SAS
http://www.superantispyware.com/and winpatrol, which as you see is very highly rated on cnet
http://download.cnet.com/WinPatrol/3000-8022_4-10129149.htmlthis is a very useful program,,, i use to use it in the past but only use it now on other peoples pc's to see whats going on and to show them how to use and monitor there pc,,,, hope all this helps,
i will just say this as well ,,, as pc's get older and more used they tend to fill up a bit with clutter and left over crap, and over a matter of years the machine will slow down,,, there are optimisers that promise to speed things up but these are all crap,,, also REG cleaners that will sometimes do more harm than good to the registry,,, when im fixing someone's pc,,, when i know all is fine i always backup the registry to my flashdrive and transfer it to one of my harddrives at home,,, because guaranteed with in a month they have used a registry fixer/cleaner and knackerd the registry,,,

just use what is called good house keeping,,, clear out the browsers from time to time, say once a week, let the auto defragger do its thing,,, use a program like Revo Uninstaller to delete programs from the pc as this will clear up all leftover reg entries aswell,,,
http://download.cnet.com/Revo-Uninstaller/...4-10687648.htmlgood luck