CPU Speed Lock @ 0.78GHz on Task Manager ( Windows 10)

[surveys2ez]

I noticed a sudden slow down in my laptops performance. Looking at task manager my CPU ( Intel Core i5-4210M @ 2.6GHz ) is only running at 0.78GHz regardless of load. I have run the Intel CPU diagnostic tool and it passed all the tests. I do not believe this to be a hardware issue as when I launch Windows in Safe Mode task manager shows the CPU running at its full 2.6GHz. I've already tried reinstalling Windows however I kept all my files, apps etc as I don't have a backup drive to save what I want. I think resetting the laptop completely would work however I don't want to lose all my installed games etc as I have an incredibly bad internet connection. What should my next step be to diagnose and fix the issue?

NOTE: I have already checked my power management to ensure all settings are at 100%.

 

[Colif]

Try doing a clean boot - read instructions and make sure NOT to disable all Microsoft services or win 10 won't boot right - https://support.microsoft.com/en-au/help/929135/how-to-perform-a-clean-boot-in-windows

it should have same result as Safe mode, its possible the cause is a start up program. Slowly re enable all the services you stopped and adding startup programs back to find cause.

I was going to say its speedstep but thats a BIOS settings and fact it runs at normal speed in safe mode makes me think that is wrong. Still could be something forcing PC to run at lowest idle speed.