booting from lan

ok , here is my problem . i have a laptop that i got from a friend to fix for him . it has windows xp tablet installed on it . he (my friend) does not know the admin password to gain access to this machine . normally i would use ophcrack or l0phtcrack to retrieve these passwords , but this laptop does not have any secondary drives (CD or floppy) . in the BIOS , there is an option to boot from LAN . i do not know how this is done . i have tried connecting it to my PC with a crossover cable . i get a connection breifly , but cannot communicate with the laptop . i have been reading a little about PXE and NetBoot , but i am still not clear on what to do . i welcome any and all advice .

P.S. i am eventually going to boot ophcrack to the laptop via external CD , but am interested in trying to do it this way first . thanks in advance .