It may be that the network is configured for desktop pc and lappy 1. Lappy 2 comes along and is different to lappy 1 and is not the networked lappy, you would have to reset all the priviledges for lappy 2 to be able to access them. At the moment the drive sharing is between desktop pc and lappy 1, lappy 2 is an intruder that doesn't have the file sharing etc set.