My question and problem is, i have 2 computers 1 of them has an ethernet card the other doesnt so i cant netowrk them via this way. They do however have usb ports. Can I connect then via this? do I need a special USB cable?
Also I do have a broadband Modem/Router which i connect to 1 Pc via usb it does have a spare ethernet port; could i connect the modem to the computer without the ethernet port by usb then connect it to the other computer via ethernet. would I then have a netowrk?
No, you wouldn't have a network. If you want a network you have to purchase a hub, switch or router(not modem). You could also run a cross-over cable from 1 pc to the other, both ways you need network cards in both pcs.... im not too sure about networking via usb though.
I know that there are USB to Ethernet adapters (both wired and wireless versions). I used to use one for my laptop which had no onboard RJ-45 (ethernet) jack. Just use one of your free USB ports on the non-ethernet equipped PC for a USB to Ethernet adapter, plug the ethernet cable into this adapter and you should be good to go (of course you need to set up any drivers/software first).
If you want to merely network the two together, get a cross-over cable as 'hunter James' suggested. If you want to create a true LAN, you will need a router of some kind to share your broadband connection.