When you add the 500GB it probably changes the boot order in the bios. With the 500GB plugged in, go into the bios and tell it to boot from the 160GB again. Option under boot order or disk/drive select.
When you add the 500GB it probably changes the boot order in the bios. With the 500GB plugged in, go into the bios and tell it to boot from the 160GB again. Option under boot order or disk/drive select.
Try reading the manual? Every bios is different. As I said, look for the boot options. Or something about selection which drive. I don't even know what motherboard you have or types of drives you have, so you will have to do the work yourself.