Reviving an Old PC from the Warehouse – A Guide to Dual Booting Linux

To bring my 10-year-old PC back to life as a working machine, I experienced multi-booting challenges while installing Ubuntu MATE. At the heart of it was the pivotal transition from "UEFI to BIOS." This post documents the complex situation and my successful journey in establishing Linux without giving up on genuine software.

Why Did I Need Multi-Booting?

This PC has been running Windows 7 installed via USB for 10 years, then upgraded to Windows 8 and 10, enduring for a long time. Eventually, it was left in storage due to its outdated specifications, but I decided to revive it as a working machine using Linux.

The issue was the assets I couldn't discard: - The original permanent version of MS Office which can no longer be obtained - The expensive genuine license for Windows 10 Pro

So, wiping the disk and deleting Windows with GPT was not an option. Thus, I had to resort to multi-booting. However, this choice led to unexpected technical conflicts.

Problem 1: MBR Partition Limitations vs Modern Linux Partition Requirements

📌 Summary of the Situation

• The SSD is an MBR-based disk with Windows installed
• Windows typically uses three partitions
• System
• Boot-related partition
• Recovery partition
• MBR allows a maximum of 4 partitions
• Installing Ubuntu MATE requires two additional partitions
• / mount EXT4 partition
• EFI system partition (ESP, FAT32 - the system partition storing boot information)

I needed a total of 5 partitions, but MBR only supports 4… right when I hit a wall.

✅ Solution

• Reduced some space on the HDD instead of the SSD to create an ESP partition
• Installed the grub bootloader on this HDD (which is typically installed on the same disk)
• Set the HDD as a higher priority than the SSD in the BIOS settings

This choice was incomplete, but it was the only method that allowed installation without destroying Windows.
I didn't need to convert to GPT, and I could preserve the genuine software.

A fantastic combination where “GRUB runs from the HDD and Ubuntu runs from the SSD.”

Problem 2: Why Didn't GRUB Recognize Windows?

After installing Ubuntu, I set the boot to UEFI in the BIOS, and GRUB did not detect Windows.

• Windows uses an MBR + BIOS-based boot structure
• GRUB is installed based on UEFI
• Since GRUB cannot chain load a BIOS-based bootloader, it recognizes Windows as a regular partition rather than an operating system (OS).
• With no OS options available, it automatically boots Ubuntu.

✅ Solution

• Disable UEFI mode in BIOS (= Legacy BIOS)
• Attempted to boot from HDD → temporary failure (grub cannot run in BIOS mode as it’s a UEFI bootloader), but this led to fallback into the Windows MBR bootloader on the SSD, successfully booting Windows.
• Attempted to boot from SSD → Success (MBR + BIOS-based Windows boot succeeded)

Ultimately, through combinations of UEFI ON/OFF and boot disk order settings in BIOS, the below “hardware-level multi-booting” was established:

It became a physical multi-booting structure that allows OS selection easily without GRUB. In practice, this improved the UX compared to the traditional GRUB method of selecting operating systems. While it may be slightly cumbersome for users who frequently switch between the two operating systems, it is an immensely satisfying setup for someone like me who primarily uses one OS and occasionally needs the other.

Takeaways

• Today's Linux enforces UEFI-based installations, but I came to understand that this is an inevitable evolution for security and scalability.
• I was able to protect genuine software while also creating a fast and reliable Ubuntu environment without losing compatibility with BIOS-based systems.
• In particular, the configuration that allows OS switching with just a switch instead of GRUB was more comfortable than I expected, and for someone like me who does not frequently switch between two operating systems, it provides a very satisfying experience.

Conclusion

The world of “UEFI vs BIOS” seemed complex and perplexing at first.
However, when faced directly, I learned that with accurate concepts and flexible choices, it is possible to protect genuine software and use Linux.

I feel a deep sense of accomplishment in installing Linux on this 10-year-old PC and breathing new life into it, allowing it to be active once again on the working floor.
I hope my experience helps someone in a similar situation, and I sincerely suggest that if you have an old machine gathering dust somewhere in your warehouse, consider reviving it for a new purpose!