Check the disks for scratches too.
But since you have 4 different disks, it doesn't sound like thats the problem.
Bad hard drive, or maybe bad hard drive cable. Try switching cables from one of the dvd drives to the hard drive....
No, it doesn't matter which port you connect the hard drive to as long as its detected. Thats old school thinking ^.^ Make sure AHCI is still turned on however.