I don't have access to my wap (I don't have the admin password, my brother is the only one who knows it), but it isn't blocking ssid broadcasting.
The xp computer is using simple sharing (I might have to change it though, and see what that does)
I'm positive all of the computers are on the same workgroup (we use home instead of workgroup or mshome)
I tried disabling the firewall on the laptop (forgot to check the xp computer, I'll have to check it when I change simple sharing)
I'm not positive, but I believe I tried changing the 128-bits encryption option, and I believe it didn't do anything.
Though I'm not really sure if the simple sharing will do much though, because my desktop can connect to the xp computer, and the laptop can also connect to the xp computer if I disable wifi and connect via ethernet. (which doesn't make much sense to me...)