I've had my computer for years. Just yesterday I turned it on and there is a
window saying it found new hardware and needs to install a modem. I haven't
put on a new modem, nor uninstalled the old one. I cannot connect to the
internet with my computer!

So - how would my modem have disappeared? The only way I can think is
through an automatic update from Microsoft.
How do I get back connected to the internet?