I wrote a post about that and it's only gotten worse.
Now let's try and fix that Dell. I can't help yet because you left out the critical information such as model numbers. You can go ahead without me since you have the machines and can head to Dell.com to see what wifi drivers have been issued.
I have a linksys WRT54G router that I have configured with WPA security. In my home the wireless network works on two machines, but on two older Dells the network shows up as WEP and asks for the password/network key. I enter it but it won't connect. Also, I cannot seem to get these tow machines to offer up WPA as a choice. Any ideas?