Explanation
The newly installed OS is x86. The x86 version of Windows 10 can only use up to 4GB of RAM. The x64 version of Windows 10 can use up to 2TB of RAM

The most likely cause of the issue is a "time drift". Time drift occurs when the clock on a computer is not synchronized with the clock on the domain controller. This can cause authentication problems when a user tries to log in to the domain. The fact that the technician is unable to browse to the secure intranet site to get troubleshooting tools suggests that there may be a problem with the network connection or the firewall settings on the desktop PC12

For a SOHO (Small Office/Home Office) router setup where the goal is to only allow specific computers on the network, MAC filtering is the appropriate solution:
* Configure MAC filtering: This security measure involves creating a list of allowed device MAC (Media Access Control) addresses in the router's settings. Only devices with MAC addresses on this list will be able to connect to the network, effectively restricting access to authorized computers only.

The best solution for a technician to implement is to disable the browser from sending notifications to the Action Center. This will prevent the random advertisement notifications from appearing in the Windows 10 Action Center, which can be annoying and distracting for the user. The technician can follow these steps to disable the browser notifications1:
Open the browser that is sending the notifications, such as Microsoft Edge, Google Chrome, or Mozilla Firefox.
Go to the browser settings or options menu, and look for the privacy and security section.
Find the option to manage site permissions or notifications, and click on it.
You will see a list of sites that are allowed or blocked from sending notifications to the browser and the Action Center. You can either block all sites from sending notifications, or select specific sites that you want to block or allow.
Save the changes and close the browser settings.
This solution is better than the other options because:
Running a full antivirus scan on the computer (B) is not necessary, as the advertisement notifications are not malicious or harmful, and they are not caused by a virus or malware infection. Running a scan will not stop the notifications from appearing, and it will consume system resources and time.
Disabling all Action Center notifications is not advisable, as the Action Center is a useful feature that shows notifications and alerts from various apps and system events, such as email, calendar, security, updates, etc. Disabling all notifications will make the user miss important information and reminders, and reduce the functionality of the Action Center.
Moving specific site notifications from Allowed to Block (D) is not the best solution, as it will only stop the notifications from some sites, but not from others. The user may still receive advertisement notifications from other sites that are not blocked, or from new sites that are added to the Allowed list.
This solution will also require the user to manually manage the list of sites, which can be tedious and time-consuming.
References:
1: How to Disable Annoying Browser Notifications - PCMag

services.msc is a tool that can be used to resolve the issue of "The Audio Driver is not running" on a Windows machine. It allows a technician to view, start, stop and configure the services that run on the system, such as the Windows Audio service. compmgmt.msc, regedit.exe, explorer.exe, taskmgt.exe and gpmc.msc are other tools that can be used for different purposes on a Windows machine, but they are not related to audio drivers or services. Verified References: https://www.comptia.org/blog/what-is-services-msc https://www.
comptia.org/certifications/a