Windows XP and Vista Sharing

I have read the messages of sharing Vista (Home Premium) and WindowsXP SP2.
I am trying to set up a network between my desktop computer (OS WindowsXP
SP2) and my HP Pavilion dv6690ej laptop (OS Vista Home Premium Hebrew
edition). Both computers use the Windows Firewall. The router is the Siemens
SL2-141 Modem router. The desktop computer is connected to the router through
a Lan connection while the laptop is connected by a wireless connection.
The problem:
Both computers are configured to have the same workgroup: MSHOME.
While the WindowsXP computer recognizes the folders in the laptop (Vista),
and can open the folders and files, the laptop recognizes the existence of
the logical drives and folders in the desktop, but does not allow to open
them, giving a message (freely translated from Hebrew):
"There is no possibility to access the drives or folders in the XP desktop
because maybe you do not have permission do so. Contact to the Network
manager(?) to see if you have an access permission.
There is not enough storage (?) to operate this process"