you will need to get a WI FI pci card ( i would stay away from the USB ones
) for the desktop.
you will need to create a peer to peer on both PC / notebook of the same name
turn off ALL firewalls even XPs built in one, for the time being
you have to have a log on account with a password on each pc, both PC's must also have each others,
if xp home , the guest account must not be disabled.
make sure in tcp/ip props that the radio button is set for "obtain ip / dns address auto"
enable dhcp in the router.
share the printer or folders
only share folders , do not share the "C:\" drive
capture printer from other pc