If you are wanting to share a broadband connection wirelessly with bluetooth then the major problem is that the range of bluetooth is only around 10m.
You would be better off going with Wi-Fi (802.11b or 802.11g). They will be a lot easier to set up, cheaper and have a greater distance.
Simply buy a wireless access point and plug it into your router, then buy a wireless PCMCIA card for the laptop and plug it in (make sure the access point and the PCMCIA card are of the same wireless standard - either 802.11b or 802.11g)
If you are running XP then use the networking wizard to sort out the settings.
This will be a lot better than going for a bluetooth solution.
p.s., there are a lot of users (myself included) of wi-fi who are members of this forum. If you have any problems with set up, you know where to come to post a question.