I'm really sorry but I just can't understand your situation. Could you restate it in a crystal clear form? Maybe use some visual aid?
[PC 1]---------X----------[Crap PC]
V
V
[INTERNET]
Something like that. And that is what I am thinking you want. You have a PC that is connected to the internet. You want to connect the crappy PC to that newer one but can't. And you have only a dial-up modem(phone jack) on the Crappy PC, so you can't use an ethernet cable? Is all that correct?
If that is what you are needing help on, then your problem won't be as simple as "connect cable from A to B." You will need to either get a networking card that has an ethernet port or get a wireless usb adapter. I believe you have a router already(don't know if it is wireless). It seems like you said your newer computer is connected to a router.
Now even if you don't have a router, you can possibly use a complex set up. With any internet connection on Windows, you can set an option that allows other computer to access the internet through that PCs connection. Of course the two PCs must be connected in a 'proper' fashion(can't just run a phone cord between the two).
So it is looking like a wireless adapter is an easy fix(if you have a wireless router), but either way here, you need a bit of $$ to make this happen. Network cards(very basic) are actually very cheap. For about $20 u can get a 100 Mbit card, and if you don't already have a router(which I believe you do) those run about $20 as well(4 port).
http://www.bestbuy.com/site/olspage...rrentprice+skuid&sc=abComputerSP&id=pcat17080
