There is one software name ip scanner available in net easily. in which u have to enter source ip and destination ip e.g. 192.168.0.0 to 192.168.255.255 now the software is scan all ip between this. now thi ip which is used by some one and if its on right now than its blinking and u right click in this ip and can explore its pc and use the share drive of it.
try it.