Thanks for the replies guys! There's never a simple PC related question is there?
Re the cable solution - hadn't realised I'd have to power up/down as well as unplug cables! Drat!
The newer XP/PC is in another room and the cable is not long enough to move the modem in there so I thought a long ethernet cable from the modem in this room to it might be the ideal answer and avoid a router. Possibly not then
Don't really want to mess about with upgrading this PC to be honest but the new PC is equipped with a 'fast ethernet network connector' - whatever that is.
Any other thoughts anyone?
Cheers