hello
do you have a wireless router ?
are you near a hot spot ( an area someone is broadcasting free wireless internet ) ?
you did say pc, so this is not a notebook you would be taking somewhere ?
do you have broadband ( DSL or cable) ?
do you have a DSL or CABL , modem / router that has a wireless router ?
As far as the card , it would be PCI or USB for a pc and PCMCIA or USB for a notebook, and a lot of the notebooks have built in wireless.
As far as the " card " it all depends if you have existing equipment and what format like 802.11 a , b or g I like netgear here is their web sit
http://www.netgear.com/
if you need a wireless router here is a netgear for $29, might be good only for taday
http://www.newegg.com/Product/Product.asp?Item=N82E16833122016
its $49 with a $20 mailin rebate