Can I use my router as a desktop wireless access card?

Basically I'm trying to split the internet with the guy next door. I can get his signal with a laptop and a wireless card if I sit near the window.

Is there anyway I can use the router I have as a wireless card (i.e. put the router near the window and then run cat5 over to the router)?

It is a linksys router capable of bridgemode. I'm just not sure what that means.

Yes.. You can.. Have a look on this link on how to make Linksys router as bridge with firmware upgrade: Using Two Linksys WRT54G Routers to Bridge One Network

)
picoHat
Home Network and Wireless Network Help

what model is your linksys router?
you can install third party firmware that will let you do that.
two of them are
http://www.dd-wrt.com/
and
Tomato Firmware | polarcloud.com

they will let you run home routers in client AP mode so they can connect to other routers.