Very slow when opening programs or accessing files

My dad's PC is running Windows 7 64 bit. Recently, the PC is very sluggish when a new program is being opened, like Google Chrome, it takes ages to open as compared to before and when files are being accessed, Explorer.exe takes a long time to load as well.

Under Task Manager, the CPU usage is around 2-5% and Ram usage is 50+%. Nothing abnormal..
I did a check of the temperatures of the components via Coretemp and it was fine.

Resource Monitor shows maximum frequency typically hovering around 40-50%. This is somewhat odd, I compared it with my own PC and mine typically shows 80-120%.

I suspected there is some issue with the processor, and when I ran CPU-Z, the core speed is around 1596Mhz. Which I suppose is abnormal as well ? The processor is an i5-2500K and I did a quick check on Google, the core speed isn't supposed to be that low.

Any idea on how to bring the Processor core speed back to normal ? Or is the issue somewhere else ? Appreciate any guidance in resolving this issue

Most CPU's has a variable clock related to load. My i5 (6600k) works between 800 an 4200 (OC).

What you facing may be due to disk problem.
Do a check disk. Open a CMD window as admin (Right click on the CMD shortcut and you'll see Run as Administrator) and type:
chkdsk C: /f

As your drive is in use it will ask if you want to schedule to next boot=Yes
Reboot

Megahertz07 said:

Most CPU's has a variable clock related to load. My i5 (6600k) works between 800 an 4200 (OC).

What you facing may be due to disk problem.
Do a check disk. Open a CMD window as admin (Right click on the CMD shortcut and you'll see Run as Administrator) and type:
chkdsk C: /f

As your drive is in use it will ask if you want to schedule to next boot=Yes
Reboot

I ran chkdsk and there were no bad sectors, only an errror - "correcting errors in volume bitmap".

Hopefully it is fine now, thanks