I want a laptop I can ONLY use for writing, with no possibility of connecting to internet. I use a netbook because it has a solid-state drive and is quiet -- but is there any way to disable wifi connectivity permanently?
Sure, go to Device Manager, disable the WiFi and Ethernet network cards there.
1) I find no such cards in my netbook computer;
2) If those cards do exist, turning them off would not in any sense permanently disable wifi connectivity, because I could turn them back on.
It's impossible that you don't have network cards in your laptop unless you disabled them in the BIOS. But if you don't, then wireless is not working so you are all set.
Of course you can turn the WiFi card back on, the only true way to disable it is to open the laptop and remove the wireless card and then damage the slot the card went in so you can't re-install it again. But then you can just add in a USB WiFi card. So then if you never ever want to have the possibility of WiFi, you'd have to also physically damage the USB ports so you can't add in a WiFi card that way. This may also damage the motherboard causing the system not to work anymore.
So as you can see, disabling the wireless card in device manager or just turning it off in BIOS or the function keys is as good as any other method short of physically damaging the computer.