Mine shows over 5 devices on the same IRQ - apparently normal for modern machines. Don't think that's your problem.
I usually manually set the Pagefile so it is contiguous. Check that the Cache is enabled in your BIOS.
Are you running Norton? Recently I uninstalled Norton Internet Security/Norton Systemworks and was amazed by the speed at which everything worked. For obvious reasons they are re-installed again.
Look at your system tray and see how many applications are running (Control-Alt-Delete) can be scary when you look at how much is running in the background - this is all an overhead to the OS.
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Hope some of that helps