If it wasn't always like that but started happening after a change was made to the computer, it's probably a shell extension or video codec causing the problem.
This guide has some detail on tracking down the cause:
If you link your account, you can also create a dump for us to look at during the high CPU usage which we can use to tell you what is using the CPU so much:
While it's happening, please go to Task Manager, then the Details tab, right-click dopus.exe and select Create Dump File.
Do that 4 or 5 times, and it should create something like:
C:\Users\<username>\AppData\Local\Temp\dopus.DMP
C:\Users\<username>\AppData\Local\Temp\dopus (2).DMP
C:\Users\<username>\AppData\Local\Temp\dopus (3).DMP
C:\Users\<username>\AppData\Local\Temp\dopus (4).DMP
C:\Users\<username>\AppData\Local\Temp\dopus (5).DMP
The files will be large, but compress well.
If sending more than one file, using the 7z format instead of zip will give a much reduced size. You can do this via the Archive Files button in Opus.
Please zip or 7z the files and email them to crashdumps@gpsoft.com.au (it's best not to post full dumps publicly to the forum).