Ok, I'm not sure how to make this work in Win 2000, as I just got mine to work in Win XP Pro.
First I'll explain XP Pro. It was really simple, I reran the networking wizard and told the system to share my dial-up connection via both the pci 10/100 and the pcmcia/pci wireless card. It told me I would need a networking bridge, and then it made one. A couple of minuets later, and one restart and I am now writing this from my laptop through the wireless nic and my shared dial up connection.
Ok, on to your problem as Win 2000 doesn't do all that XP stuff lets try some other things...
First do either network card show problems in the device manager?
Second, are you running current drivers?
If yes to both of those, try rerunning the networking wizard.
Make sure they are both listed on the same network name (I.e. mine are both on the "home" network)
Try rescanning with both in ad-hock (unless you have an Access Point)
Remember that 2000 does not lag at start up to set up the network, and that it can actually take up to 2 minuets for 2000 and XP to fully be network ready. So if both your machines are searching for an IP, start one up, and then after you can view the network properties try booting the second.
A note about ad-hock, etc.
Basically, there are two wireless modes.
Infrastructur, for use with an Access Point
Ad-Hock for use without an Access Point
Ad-Hock is sometimes also refered to as 802.11B ad-hock (which is just a slightly newer modified ad-hock that is supposed to be a little better, but both ad-hock and 802.11b ad-hock should be compatable.
Ok and finally my best advice, as this was my problem with 2000 when initially setting up a network...
Make sure your Laptop and Desktop think they are different people. Mine were both under William J Sullivan. So they couldn't see each other because they both thought they were the same machine. And I don't mean the network/computer name, I mean the windows login name for Win 2000. So you may need to go into the control panel into user accounts and rename one of the machines, or log on as a different user.