Windows 10 slowdown and extremely long boot time

Question

Yesterday a HP ProBook laptop was running fine, with 8GB RAM and Intel Core i7-6500U 2.5GHz CPU.

Today morning, the Windows 10 machine was extremely slow. Windows task bar was not responding. Using some OS features line network manager wasn’t possible. So decided to reboot the machine. After rebooting, the windows got stuck at the loading page.

1. I hard-reset the machine, and used diagnostic tools, but they didn’t show any problem.

2. Pressing F8 at boot time, i.e. safe mode, led to automatic repair, which would eventually end up in a blank/black screen.

3. Finally, I rebooted again and waited so long for Windows loading to finish. After some long minutes finally Windows showed login page.

The Windows is still slow, but it is unstable. Opening an application might take more than 2 minutes, maybe 3 or 4 minutes.

This is NOT the first time I run into such slowdowns. I wonder whether this behavior is occasionally expected? How can I prevent such slowdowns?

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Laptop has HDD:

UPDATE

Two days later:

Suddenly, I run into the blue screen. I wait long but it is stuck at 0% Complete. I restart manually. Restart takes maybe 15 to 20 minutes. Then I receive a login screen with no input field for password! I restart again, this time it's faster. I get a login screen WITH a password field. I login and opening any application takes 2 to 3 minutes.

As suggested by the accepted answer, probably I'm going to totally replace this OS =(

UPDATE

It is more than one month since I reinstalled Windows 10 and deleted all the old partitions which were MBR-based and created new GPT partitions. During this period, the new Windows 10 is responsive. I'm satisfied so far :)

Answer 1

Open Task Manager: CtrlShift~

• On the Details tab, order by CPU or I/O usage to see if some process is using up resources. (Right-click on the column headers to add I/O read bytes and I/O write bytes if need be.)
• Click on the Startup tab to see if some process has impact during boot.
• Check for malware with an additional AV tool, such as Malwarebytes or from a boot disk, e.g. Kaspersky Rescue Disk.
• Also check if you the internet is a bottleneck. If your PC is syncing large amounts of data with OneDrive, Adobe Creative Cloud and other online services, then that could slow responsiveness. Temporarily disconnect (e.g. Airplane mode or unplug Ethernet) to see if the PC behaves better.

Also try running an alternative OS from a USB flash drive, such as Ubuntu. If that works well, then you know the issue is in Windows or the SSD. You can test the SSD from BIOS or from the alternative OS.

If Windows is the culprit, reinstall from the Windows ISO (or, if the alternative OS works better, install that instead).