here is the jist of my very strange problem...
I had an old laptop hard drive(120gb toshiba) which was pulled working out of a laptop and placed into an enclosure. it worked fine for a while and saw little use only as a backup drive. one day, it started clicking. plugging it in just resulted in click....click....click... and nothing else. I assumed the drive was dead(it was about 5 years old) and put it in a drawer. about 6 months later the harddrive in my current laptop(500gb seagate) was getting errors and failing diagnostics, I couldn't warrenty it yet so I ordered a new hard drive(250gb wd blue) under the assumption that I would stick the new drive into my laptop... load windows and continue having the functional laptop I needed. the old drive which hadn't failed yet would go into my enclosure and I could backup my data from there. once I pulled the drive from the pc it went right into the enclosure with the same result. click...click... click... So I thought maybe my enclosure is defective... so I ordered a new enclosure, a different brand too. same result from both drives. finally the day to warrenty came so I pulled the 250 out.. replaced the old 500 and it booted up perfectly. putting the 250 in both enclosures wielded the same results this was a barely month old drive.
I have tried multiple cables. 2 different computers(an asus i5 and a sony vaio p3). on both windows 7 and puppy linux. and 3 hard drives. I must be missing something unless I have just gotten super unlucky on enclosures. all the hard drives seem to work in a pc but not in any enclosures. any thoughts?