My post Reinstalling Windows concluded with “Right now the laptop is just a Windows system. I suppose I will turn it into a dual-boot system by adding some flavor of Linux, probably Debian or Ubuntu.”

So I went ahead and tried to install Xubuntu alongside Windows on the system. The attempt to install GRUB2 on /dev/sda failed. A quick look at Google suggested that I try a Boot-Repair-Disk. I have such a disk and I have used it successfully several times, but it failed here. The error message did not lead to anything useful on Google. I thought it might be something with the SSD, so I repeated the whole process of installing Windows and then trying to add Xubuntu afterwards. No joy. Fiddling with BIOS/UEFI settings went nowhere. My guess is that reinstalling Windows did something in the Windows boot partition that caused it to reject GRUB2. In the distance past I had been able to make this a dual boot system, but that was with the original Windows 10 installation. I thought about reformatting an SSD to use MBR rather than GPT might help, but I could not make myself take such a giant step backward. Without GRUB I was effectively left with a Windows 10 system. I then tried another blank SSD and installed xubuntu on it. No problems with GRUB2 here. The system booted and was usable

This is an old (2011) system and really not worth the effort I had been putting into it. Apparently I could have this be a Windows system or a Linux system, but, unlike so many systems I built over years, not both. I settled on Xubuntu. This is release 22.04 (Jammy Jellyfish) which will receive full support for 5 years, into 2027. Windows 10 will not be supported after October 2025 and this machine will not support Windows 11. So the systen will have a longer useful life with Linux. I was never happy with the performance of Windows 10 on it anyway.