Try these steps assuming it's a wireless network card and WindowsXP:
- use a computer with internet access to download latest drivers for your NIC from Linksys
- use a flashdrive, burnt CD or any other medium to copy the downloaded driver package too your offline machine and uncompress it
- install the NIC through the Windows Add Hardware wizard and point it at the driver package folder with drivers in it
- use Windows wizard to list and connect to wireless network
For more specific steps, we'd need to know which Linksys network card you are trying to install.