I've only had this processor for about 3 months so I don't really know if this is normal. While rendering HD videos in Sony Vegas Pro 10, is it normal for all of the cores to be running between 90 and 95%? According to the Intel CPU Usage Desktop Widget for Windows 7.
Yes! That's what the CPU is there for Most rendering/encoding programs are optimized to be massively parallel, i.e. built to be scalable and run on tens, hundreds, or thousands of cores. So this is a good sign--unless you're having heat or noise issues.
This is old, but just to give you an idea of how much the CPU does:
It is very normal for rendering to call upon all cores of your computer, 4 cores all running at once will get the job done much quicker than 2 cores at 100% or 4 cores at 50%.
If your doing other tasks at the same time and the CPU usage is causing an issue, there's usually a way to limit the CPU usage so rendering doesn't hinder other tasks. Although obviously this will then increase the render time aswell.