I'm not sure where you're looking, but there's no software required specifically to use a Linksys wireless access point or router. There are drivers for wireless cards and devices that plug into your laptop, but nothing unique to talk to the router.
The terminology isn't perfect, but good enough.
You have three choices:
Plan A. A wireless access point such as a WAP54G. A CAT5 cable goes between the WAP54G and your BEFSR41 router. Configure the router with an SSID and encryption key, and you're done with the access point. Of course, you have to setup some kind of wireless device on your laptop and give it the same SSID and encryption key.
Plan B. You can purchase a wireless router and *REPLACE* your BEFSR41 router. A good choice would be a WRT54G. The configuration of the wireless router is very similar to the BEFSR41. I believe that all the features of the BEFSR41 are also in the WRT54G. Cost of the WRT54G wireless router is about the same as the WAP54G access point.
Plan C. If you insist that you retain your BEFSR41, then you can also use a WRT54G wireless router as an access point by simply ignoring the router section. You will need to:
- Setup the IP address of the WRT54G so that it doesn't duplicate your BEFSR41. For example, if your BEFSR41 is at 192.168.1.1, then the WRT54G should be configured to 192.168.1.2.
- Disable the LAN side DHCP server. The DHCP server in the BEFSR41 will take care of assigning IP addresses.
- The WAN port of the WRT54G goes nowhere. This effectively disables the router section of the WRT54G.
- Run a CAT5 cable between a LAN port on the BEFSR41 and a LAN port on the WRT54G. Be sure to use the cross-over connector on one end.
Personally, I would suggest you purchase a wireless router such as a WRT54G and select either Plan B for simplicity, or Plan C to preserve your existing router.