Happy 4th of July!
Thanks Vostok4 and Noth. Still struggling. I'm not well versed in Ubuntu.
I tried the USB route - formatting it in FAT32 and downloading Ubuntu on it, but on a Mac (could this be a problem?) and it makes me nervous; the only PC I have is the Ubuntu one.
So far my progress is minimal - I have the Ubuntu installer on a USB but the computer fails to boot from it.
1. If I simply turn on the computer, with or without the USB stick in, it goes straight to the "rescue grub" window.
2. Holding any key - only F12 brings me a bit "closer" to having some choices, but again, it gets stuck.
3. I changed the order of booting, so that the USB should be opened first. - nothing
I am still looking for solutions.