On Thu, 14 Jun 2018 15:26:39 -0700 (PDT), wrote:

Every once in a while it disconnects.

It would be helpful to know the maker and model number of the wireless
router or "gateway". Some of them are notorious for being unable to
maintain and reliable connection.

When I go to "Connect to" it can't find any networks.

Oh-oh, that's bad. Kinda sounds like your unspecified model Gateway
laptop has a problem either in the hardware, wireless drivers, or in
the operating system. I can't tell from here.

Vista is a PITA mostly because Microsoft and vendors are unwilling to
fix their drivers because of the small user base.
https://netmarketshare.com/operating-system-market-share.aspx?id=platformsDesktopVersions
Vista is showing 0.40% or platforms in use.

This last time I unplugged the MODEM or whatever you call it to
see if it was putting out some interference and Windows could
still not find any networks.

Not finding any networks is not caused by interference. Transmitters
are not on continuously. There are guard times between packets, where
broadcasts can be heard by even the most obnoxious wi-fi interference
generators.

Later it found some neighbors' wireless and displayed it though
I can't connect because I don't have the password/key.

How much later? Did you reboot before it found the neighbors?

Do you have another wireless client device other than the Gateway
laptop? I suspect that it might not be very sensitive and is having
trouble hearing anything. Maybe the U.FL antenna connectors fell off
the wireless card? If the other device sees multiple SSID's with good
strong signals, while the Gateway hardly sees anything, then there's a
problem with the Gateway.

Customer arriving with checkbook in hand. Later...

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558