I have three machines running Mint. I love it, it will really bring new life to an older machine. The only one currently running is on my sons laptop, I need to check it out in the morning. Mine are dedicated machines for ham radio and have not been on in a few weeks.
Not to denigrate Mint, but if you are looking at working with older machines there are certain distros out there specifically designed to work with older machines, even those with quite limited resources.
In rough order of less resource demands, here are a few:
1. AntiX and/or MX-14
2. Mepis 8.0 (yes, it’s older. It works.)
3. uberstudent 2.0 lxde
4. ultimate edition lite
5. Aptosid Thanatos xfce i386
6. Linux From Scratch (LFS)
7. Damn Small Linux (DSL)
Among others...
Running gparted/GPT from a bootable Rescue CD (System Rescue CD is highly recommended) to partition the drive(s) prior to installation is most strongly advised. PartImage also is helpful to recover from any difficulties in the future.
Oh, and there are also some kiosk Linux versions you might be interested in as well.
Have fun!
The bad operating system ISO files were available for download only on Feb. 20. If your son's computer had Mint 17.3 installed before then, it should be OK.