i want to attach two sata harddisk at same pc

i have two CPUs. each one have one SATA harddisk and already set up windowXP service part 2. but one of the computer can not get window.i mean, cannot appear window xp. so i want to backup data from bad SATA harddisk. i attached this SATA harddisk to another SATA computer . but window did not appear. how should i do to take backup from bad SATA harddisk?