I'm adding another sata hdd to my system soon, and am just wondering since there is no master/slave etc. Does the system just assign this new drive a drive letter automatically? How does it know which drive to boot from etc?
You can go into the BIOS and select the boot order. Select your OS drive as the first boot device. By default, the next drive letter available will be assigned. You can change the drive letter in "Disk Management" to whatever letter you want (that's available).