I bet you do not need or want any proxy server.
I bet you question really is how to get internet connected, right?
first off what OS is this, XP> we can not see you, your PC nor your OS. (whats connected to PC, nor if it has wifi options)
is this IE11 your browsers , cant guess that either,?
why not use an Ethernet, Lan cable CAT5/6 and plug in the PC to the router and it all works like magic,
that be first.
if the PCs lan jack (ethernet ) is dead. (and other PCs work on your router) do they./
then we go to device manager and look
see that? then see if the lan chip has driver.
network marked, red/yellow or unknown is bad.
if missing the get it from HP.
HP has zero support on old PCs, it's too old, its in fact 16 years old. support ended . 2007 (17-10 = x)
came with 10/100 Ethernet, new (spec sheet says)
slow. that is.
but what chip that is , is very hard to find out this old
why waste time and money on PC worth $5 used.?
it came with windows 2000 or XP new. which is it?
if the driver is good, or the unknown chip there, ethernet
the when you connect to the router the connection made automatically
then running relic old IE 6? you see proxy question
tell it no, and that sets automatic , gate way ip address to your router. and just works out of the gate.
install firefox v56 and its more easy.
to run and not get bogged down in proxy settings.
avoid IE versions below 11, as all OLD IE's, are virus magnets and zero support, use Firefox, on all old PCs, not updated to W7 !!!
IE = internet exploder browsers)
show just getting a connection, only. browsing is a whole other matter, and 20 browsers free are common.