If both HDDs are recognized in BIOS now:
If I remember correctly for SEAGATE drives you should be able to use discwizard that will ask you for source and destination disks, perform the cloning and will also switch boot sequence in your BIOS so that new disk become systems disk.
Pretty sure that the equivalent for WD drives is Acronis True Image WD Edition but I am less familiar with it-check the WD website.
Recommend a backup of your 'source' 160gb disk before you start or at least any personal files. I've never lost anything with discwizard but better safe than sorry.