On my Win7 machine, I have installed Microsoft's Virtual Machine that allows me to run WinXP applications. Two weeks ago, i.e. mid-July, it was working fine. Today, 29 July, it is essentially useless. When one examines the processes running on virtual WinXP, it shows NSBU.exe essentially running at 100% on both processors. When one examines the processes running on Win7, the host, it shows WinXP as consuming 100% on both processor.
Norton Internet Security is installed on the Win7 machine. I do not think it is installed on the WinXP virtual machine; there is no need for it on the virtual machine because it is not used to surf the Internet.
Today, so I could use WinXP, I killed the NSBU.exe process via control-alt-delay from within WinXP.
Obviously, a longer term solution is needed. The host Win7 machine has been given plenty of time to check and install updates to the Norton software.