Unless I mis-read the orignal post what's wanted is the way to physically connect the laptop & PC ... we know the laptop has built in wireless and the PC is connected to the internet with ADSL via a cable.
FWD wants to get the laptop into the loop without getting wireless capability on the PC....
If we knew how the internet "cable" connected to the PC/phone we could better advise.
Thats why I'd asked earlier "Where exactly does the lead from your telephone socket go? "
Options might be:
1. If the PC's internet conx is via a wireless enabled modem router then just wireless conx through that (guessing not so which is why the question!) [This option is good as laptop can conx to internet without PC being switched on].
2. If the PC's conx is via a modem router with ethernet ports then a standard networking cable would allow the laptop (most laptops for some time have had RJ45 ports) to be connected to the router that way and share the internet conx. [Again a good option which means the PC doesn't need to be switched on].
3. If the PC's conx is via a USB modem and the PC has an RJ45 port then use that. If it doesn't have a network (RJ45) port then it won't work without something being added! [Worst option, IMHO, as it will need the PC to be on to connect to the internet].
If it needs the PC to be provided with the ability to connect to the laptop then I'd suggest going for a PC wireless PCI card, as long as there's a spare slot for it!!! They can be had for less than £14.00 these days.
Of course this is what the original post asked to avoid if possible!!!!
Actually getting the two talking to each other & the internet is not really difficult once you can actually connect them......