//Windows 7 64x opera 42 42.0.2393.85
i had the same problem and i solve it my going to task manager-process-show processes from all users-and if you see a svchost is taking up a lot of cpu right click and go to services,then try and find the service and stop it.
for me the service "Windows Update" is starting automatically and its destroying my 2 core cpu.
if you have a similar problem go to the task manager-services tap-services...(bottom right)-then you find the Windows Update service-click it and in the menu and in the startup type switch from automatic to manual and you're done
if the service starts you can go to the services and stop it
!!WARNING!! don't stop ANY services without doing you're research...i did it once and i ended up struggling to fix it with a command prompt from the windows troubleshooting future.