Somewhere in your bios you will have a boot option for which to boot first. If there isnt an SATA selection its sometimes listed as raid. Set this to IDE. This is a differenct screen then the boot priority of cd,DVD, HDD,USB... screen
Which motherbd do you have?
honestly, odds are the sata drive is the faster of the two and I would recommend booting from it and using the ide for backups ect.