Unless you are using Windows XP service pack 2 or greater you may not get it working.

Most current Drivers and cards require XP and service packs to work properly,

A wireless card alone cannot access the Internet. You also need a broadband modem from your Internet service provider and a router. The telephone modem that came in the computer was for dialup Internet and cannot use wireless. It is not a broadband modem.  If you still have dialup you cannot use wireless.

If the home router's signal reaches the camper, you might not need a second one.

ok let me try and explain i already have a wireless connection in my home i was just trying to add another computer onto myhome network, do i need to have another wireless router in my camper in order to get my computer in there to be able to connect wirelessly?

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Highly unlikely that your router signal can reach the camper because of distance, objects and walls between. If you want to add another computer to your home network in the house, position the desktop close to your router. Then you use an ethernet cable from the network card in the computer to one of the ethernet ports on your wireless router. A wireless router can handle four ethernet connections. Wireless is used more for laptops that can move around (that might work in the camper) or desktops that are not close enough for a wired connection.

Sorry about the misunderstanding in my other post. I guess you meant the desktop came with an ethernet network card.