Partners Laptop loosing connection to network drives.

Hi All, We have 2 laptops in the house and one xp desktop machine, Both Laptops are Win7 64bit. The XP Machine runs like a server sharing one 3TB External HDD and one 80GB internal HDD The XP Machine is Wired and the Laptops are Wireless. On my laptop I can Access The Hard drives and use map network drive to use them in my computer. On my partners laptop I Do the same but then her laptop...