Need advice for installing ChromeOS Flex from usb on my old pc

You can use the official browser extension to make a chromeos flex bootable usb.

MultiBootUSB is a tool for create ChromeOS Flex usb installer drives and other bootable USB drives. It transforms a single USB flash drive into a multi-system boot tool, enabling you to launch multiple operating systems without reformatting the drive each time.

User Guide: First download the image file, then launch the software. Next, select the target USB drive, choose the ISO files to add, and click “Install Distribution” to create ChromeOS Flex usb installer. This process can be repeated to install multiple operating systems on the same USB drive. It employs GRUB2 to manage the boot menu, allowing you to select the system to boot from when the drive is inserted. Its core advantage lies in enabling a single USB drive to support multiple operating systems.

It is suitable for those requiring portable multi-system booting. Overall, it is a commendable piece of software. I believe this software would serve as an excellent solution.

Since you have Windows 10 running on that 8-year-old PC, you're in a great position to create the installer directly from that machine.

What You'll Need If you want to Install ChromeOS Flex from USB:

• Your 8-year-old PC (running Windows 10)
• A 8GB or larger USB drive (everything on it will be erased)
• Internet connection
• About 30-45 minutes total time
• install ChromeOS Flex from USB

How to Install ChromeOS Flex from USB on an Old PC Using Windows 10

Step 1: Prepare Your USB Drive

Step 2: Download the ChromeOS Flex Image

Step 3: Download BalenaEttcher

Step 4: Create the Bootable USB with BalenaEttcher

Step 5: Boot Your Old PC from USB

Step 6: Install ChromeOS Flex from USB

Step 7: Finish and Set Up

The official Google Chromebook Recovery Tool is a free, official browser extension developed by Google to assist users in effortlessly create ChromeOS Flex usb installer. This tool operates on any operating system, featuring a streamlined interface and official technical support.

Step 1: Open your browser and visit the Chrome Web Store.

Step 2: Search for the software within the store.

Step 3: Install the extension into your browser and await completion of the installation.

Step 4: Click the extension icon in your browser toolbar to launch the tool.

Step 5: Follow the on-screen prompts sequentially: select the image file, choose the USB drive, and confirm to begin create ChromeOS Flex usb installer.

Step 6: Once the writing process completes, safely eject the USB drive.

As an official tool, it offers high compatibility and avoids the risks associated with third-party tools. Its straightforward operation makes it suitable for all users wishing to write to the system

Fedora Media Writer is a free and open-source tool that enables you to create ChromeOS Flex USB installers on multiple operating systems.

How to create a ChromeOS Flex USB installer

1. Download the image file
2. Open the software
3. Click Custom Image
4. Select the downloaded image file
5. Choose your USB drive
6. Click Write to Disk to create the ChromeOS Flex USB installer

Cons

• Slower writing speed compared to some dedicated flashing tools.
• May fail to boot on some UEFI-only devices without proper boot order adjustment.
• No advanced formatting or repair options for problematic USB drives.

What about the DD for Windows if you are going to install ChromeOS Flex from USB on an old PC? 

First, you'll need to download the ChromeOS Flex image from the official Google website or other trusted sources. This image file is typically in a .img or .iso format. Once you have the image, you'll also need to download DD for Windows, which is a free, open-source tool that provides a simple graphical interface for using the dd command. When you open DD, you'll select the downloaded ChromeOS Flex image as the source, and your USB drive as the destination. Double-check all selections carefully; selecting the wrong drive can result in data loss on your other drives. After confirming, you can start the writing process, which may take several minutes.

Once the image has been successfully written to your USB drive, you'll need to prepare your old PC for the installation. Restart the PC and enter the BIOS or UEFI settings—usually by pressing F2, DEL, or F12 during startup. Change the boot order to prioritize booting from the USB drive. Save your settings and reboot the computer with the USB plugged in. If everything is set up properly, your PC will boot from the USB, and you'll see the ChromeOS Flex environment load. From there, you can choose to try it in live mode or proceed with installing ChromeOS Flex from USB permanently onto the hard drive.

Since ChromeOS Flex is designed to be lightweight and cloud-centric, it should run well on an older PC that's about 8 years old. During the installation process, follow the on-screen prompts to format and install ChromeOS Flex from USB on your device’s storage. After the installation completes, your PC will reboot into ChromeOS Flex, allowing you to set it up with your Google account and start using it. This method provides a free and efficient way to breathe new life into your aging hardware, especially now that Windows 10 support has ended, and ChromeOS Flex offers a fast, secure alternative.