|Hi BeeBee, here in the UK:-|
a) the router/modem is best connected to the master telephone socket
b) connecting the pc directly (by ethernet cable) to the router is better than wifi.
Sdfox's advice is good, however if the pc location is remote from the router, consider using wifi:-
i) a usb wifi dongle - cost about £6.
ii) if pc has no usb or usb 1, a usb 2 card - cost about £6
With a Pentium 3, due to cpu speed. you may find problems with programs such as Skype. e.g. the video side may not work but sound will be ok.
Please advise back on progress.
As a matter of interest, where are you located? I am in Hammersmith, West London.
Good Luck - Keep us posted.