What OS's are on them (XP Home?)
Oh, wait, I think I might know what you need to do.
Go to Network Connections on both computers. Select the active network (one of the "Local Area Connection"s on the desktop, "Wireless Network Connection" on the laptop). Right click, go to "Properties"
There's a list of stuff (under the heading "The Connection uses the following items
. If you don't see an entry that includes something along the lines of "IPX/SPX/NetBIOS" (IPX and NetBIOS being the important bits), click "Install...", select "protocol", then select the IPX/SPX/NetBIOS-type option. Once you do that on both, you should be able to access one computer from the other.