BIOS configuration must be proper, as it performs hardware initialization during the booting process (power-on startup) and provides runtime services for operating systems. If BIOS is not configured correctly, it will affect your PC's startup process. Make sure your first boot device is a system hard disk.
Let us check how to change the boot order in BIOS to Fix Windows 10 if it is slower after the update.
Step 1. Start the computer and press ESC, F1, F2, F8, or F10 during the initial startup screen. Depending on the BIOS manufacturer, a menu may appear.
Step 2. Choose to enter the BIOS setup. The BIOS setup utility page appears.
Step 3. Use the arrow keys to select the "BOOT" tab. System devices appear in order of priority.
Step 4. To give the boot sequence priority for the drive, which would speed up the Windows 10 boot time, move it to the list's first position.
Step 5. Save and exit the BIOS setup utility. The computer will restart with the changed settings.