Hi there

I'll give it a go

If it is a standard Linksys this might work.
Connect Ethernet cable from laptop to router.
log into the router by typing in its gateway address, you can check this by looking at the "support" tab in the Status box of the Ethernet network connection.
It might be 192.168.1.1 or 192.168.1.2
Default user name is normally "admin" and password is "admin" by default.
If you get in the router go to the "Wireless" tab and select "Wireless Security"
I would suggest selecting the most basic security "WEP 64bit" as almost all client adaptors support this.
Then enter a 10 digit Hex number, These numbers would include "0123456789ABCDEF"
Then select save settings and try and log in with your laptop with the wireless card.
If this does not work try and disable the security.
If it still does not work then a factory reset is the last resort.

Then i suppose you could read the manual.

All the best
Dale