I have a Acer 5515 that I bought used about 5 years ago. It started with Vista Basic 32bit locked in. I had to go into the bios to get it to allow me to switch it to Windows 7-64bit.
I run Windows 10 64bit on it now. It works great. I did have to add 2 gig of memory to it to make it work as well as it does, but, memory is cheap.
Personally, I’d upgrade it as far as you can.
On another point, I have a second hard disc for it that I pop into it and run Fedora on it. It’s time to upgrade that drive.
If you don’t like 10, then go to 7 and hope your friend will be happy.
If it was my laptop, I would indeed upgrade the memory and upgrade it to Windows 7, but that's not my call. I'm putting Vista back on it, update Java, Flashplayer, install Microsoft Works, and afterwards call it good.