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Check out this guide to network activity in the Windows Resource Manager, and how to look up processes you don't recognize that are using bandwidth.
Stop svchost.exe from stealing CPU cycles - Advanced topics
How to find out from where the browser is loading Adobe Systems' Flash Player. This detective work is especially important when dealing with portable versions of Firefox.
More about the excellent Process Explorer program.
From Daniel from Kyte.TV to free antivrus, to sending pages by Bluetooth.