On Select Disk window, do you see any disk to choose?
Yes. :( when I try to turn on time machine, another window pops up like it wants me to select a disk and the "use for back up" button is grey and nothing appears there. I got in the system profiler to check whether all the hardware components appear there and under the ATA option it says "this system does not contain any AtA devices installed..." I a new with mac and I really don't know how to solve things in this platform :( i used to be good at solvng things in lousy windows. The system obviously has an internal disk