hope in right group.....

dad found a good computer in w/end garage sale,, has it set up next to his usual one, and wants
it to have internet access.
made enquiries, and you cant just buy a splitter or whatever for the cable that comes out of his
broadband modem to plug into the latest one.

the two computers are less than a metre apart,,,,,,,,,, both are running xp,,,,, exactly what
is it that he needs to do to have the second computer to access the intenet using his existing
modem?
i have heard of a single cable connecting the two computers,, but apart from that, i have no idea
where to go or what to do.

tia for help.