Well, I would use one of the disk utilities to delete all the partitions
first. Then either create a single partition or multiple partitions and
see if things improve. A good free tool to do this with is EaseUs Home
edition, which you can download at http://www.partition-tool.com/

I would also run HDAT2 from Hirens boot CD and see what it says about
the drive. You can download a zip file, which will make an .iso file,
which will make a bootable CD at
www.hirensbootcd.org/files/Hirens.BootCD.14.1.zip