Well, how did you install the kernel? You compiled it yourself?
If so, you've to select the following:
<M> Generic IEEE 802.11 Networking Stack
<M> IEEE 802.11 WEP encryption
Device Drivers --->
Network device support --->
Wireless LAN (non-hamradio) --->[*] Wireless LAN drivers (non-hamradio) & Wireless Extensions
<M> Intel PRO/Wireless 2100 Network Connection
And I think you've to get the firmware too, make a search on this forum, i'm sure you'll find the answer.