Valuable tips for work with Windows based computers (desktop or laptop).

Windows OS in your PC cannot see USB connected external drive (i.e. HDD)

Go to search line, type "cmd", click on cmd, inside type "disk manager" and there change the drive letter of the drive in question in the list of the drives, even with exactly the same letter. Do not think, just do it and click OK. Result will appear in a split second.

USB flash drive is not visible in boot menu of BIOS/UEFI

It will be if you'll prepare it as bootable and fill with Windows .iso file using latest RUFUS software setting partition type to "GPT" and file system to "Fat32". The UEFI automatically will detect it afterwards. But to boot with this flash drive you will need to set it as the first device to boot from (top one) in the BIOS/UEFI boot menu and reboot PC straight away.

Notes:

UEFI (BIOS) of your PC blocked by password you do not remember

It wont be blocked if you set the supervisors password from the first day. Not the empty space or something like that, but proper password with some digits or/and letters, just make a note of it making sure you do not lose it. In case it's blocked already, firstly you can go to support page of the official web site for the manufacturer or seller of your PC (desktop/laptop), some of them might give you unlock password free of charge especially if you still have a Warranty and can prove the ownership of the PC. In other cases they will charge you 100 USD just for giving you few symbols of the unlock password after you send them the digital key you get from BIOS/UEFI when you enter wrong password. But in your shoes better to go to Ebay, where you could find the same service for 40-60 USD, or just find on the net via search line: "unblock bios/uefi password for (here just include your PC name and model)". Very quickly you could find good samaritans, who will do the same (provide you with the password after receiving your digital Key) but for just 10-20 USD and sometime you could find the web sites where you could do that free of charge (if you are lucky not to have one of the latest PC model).

Additional information to already spoken about:

"Acer" support is almost non existent as they do not take into account your Warranty, your situation and ask you only for money (100 USD). If you start arguing with them they are trying to ignore you and if you insist, they send you a message, half of it hard to understand at all (they do not know either proper English or their job or support agents just do what company said). It looks like Acer thinks that when you purchased PC from them it still belongs to Acer and you just use it for the time being. Besides, the hardware inside "Acer" laptops is good enough (don't get us wrong), but the operating system is very sluggish and in every case you buy their PC you need to replace the OS with the new, clean one. That's when you need an access to UEFI/BIOS.
Note: After replacing original HDD for SSD the speed of the operating system and the work of the PC will triple. After you replace original Acer preinstalled OS the speed of your PC will rise another 5 times or more and you will have your hands fully on all the OS settings.

Additional question: What is the reason for such secure login into BIOS/UEFI?

Actually it's a very good idea to make it password protected especially for any settings change. Some bad people might nick your laptop and use it as they want. For the same purpose the include password protection into Operating System (Windows 10 these days). But there is a problem. They should make provision for owners to easily override these settings and turn off password protection if they wish to do that. That is legal right of the owners of the product they acquired.