20% of my backup drive has data that I can't access

Have you tried a partition manager such as Paragon Partition Manager or Easeus Partition Master?  Usually these can extract more information about hidden partitions than Windows.

First of all, it is pretty bad practice to use only one drive to backup to.

In your situation I'd at least get one more (of not two) drives to which you can backup to. After that depending on whether you need your old backups again or not, I'd delete the partition on your old backup drive.

Thanks for your responses.

I don't have any partitions set up on the drive, so would a partition manager still do anything for me?

rindi, I completely agree. The drive under discussion is one of 3 drives I use for backing up data. I'm not having a problem with the other 2.

When you say to delete the partition on my old backup drive, first-how do I determine if there even is a partition because I don't think I set one up?

Before I got the last message, I installed EaseUS Partition Master and wiped the remaining data from the drive. Funny thing though. Even after rebooting, my computer is not recognizing the fact that the drive exists. I turned the drive off and turned it back on and got an audible indication from the computer that it realized something had happened but yet the drive is still not showing up.

What do you suggest?

it looks like the drive has a problem, so i would run a diag on it  - to know it's status : http://www.tacktech.com/display.cfm?ttid=287      

you can also test by booting from a live knoppix cd -  and see what that reports :

ftp://ftp.kernel.org/pub/dist/knoppix/KNOPPIX_V6.4.4CD-2011-01-30-EN.iso 

I played around with EaseUS Partition Master and created a partition and reformatted it. Now the drive displays correctly. Thanks for your help.

I was slightly premature on that last comment. Since appearing like everything was okay, the drive in question was not displaying twice when I booted up. I performed a backup on it after it finally displayed and now it is not showing up anywhere again.

Is there any way to start from scratch again and load it as a new hard drive? I already tried turning the hard drive off, unplugging it from the PC, shutting down the PC, rebooting and then plugging in the hard drive. My PC gave no indication that anything had happened or that the hard drive existed.

I am reluctant to start a four-hour marathon on diagnosing and downloading software to determine what may or may not be wrong with the drive; since the drive had worked flawlessly and was always on for over one and a half years. These problems only happened when I used the recommended EASEUS Partition software to try to get rid of the 200GB of space that could not be used or viewed.

I need some hopefully, quick fix suggestions.

>>  I am reluctant to start a four-hour marathon on diagnosing and downloading software to determine what may or may not be wrong with the drive; since the drive had worked flawlessly and was always on for over one and a half years  <<  i know how you feel
however - i like to start from the beginning, then proceed
if you start halfway in the process, you risk missing the relevant step, and have to restart from the beginning later..
and yes- it takes time - but it's  risky to try to repair a bad drive - you cannot know what will happen

so i recommend :
-backup your data
-test the drive - and if ok, depending on what you want, run repairs, or start from fresh

Understood.

What software would be your suggestion for running the tests? is or anything that comes with Windows 7-64 the environment that would accomplish the objective?

i posted the diags above, you have to select the one for your disk brand -what's yours?
personally, i use these diags from a bootable cd UBCD : http://www.ultimatebootcd.com/      

I am using Fantom which I believe is by Micro Tech. even on their site, there is no download diagnostics or anything. What I did was scanned the disc and it came up with no errors.since it is been behaving itself for the last couple of days. I will just leave well enough alone and keep my fingers crossed.

that's the enclosure - i asked what DISK see properties in device manager

See the attached screenshot, but I can't tell which drive I am looking at.
disk-drives.jpg

The top four are either USB sticks or is your Card Reader (probably with no cards inside). The next two look like internal seagate drives, the next one is probably the one you are talking about which uses a Western Digital WD10 EADS-65L5B1 USB Disk, and the last one is also a Western Digital WD10EAVS-55D7B1 which is either also an internal SATA disk or an external eSATA disk. Check the Western Digital site for diagnostic tools. There should be a Data LifeGuard utility available you can run on external disks.

yes it looks like the WD10 EADS-65L5B1  is it
now -these diags mostly do not run on usb devices, you have to connect them directly to sata port
in windows - you can run chkdsk - but on an USB device it will take VERY long
you have a backup of it ?  if not time to take it

The WD diags have windows versions that can test USB drives, but I don't know if they will also run on USB cases from other manufacturers (I can't think of any reason why they shouldn't though).

Here's the drive situation:

I have 2 "normal" internal drives, and 2 internal SD card reader/drives (?) And 2 internal CF card reader/drives. I only use the SD and the CF drives for downloading images from my cameras.

On the external side of things, I have–

1 750GB LaCie drive
1 1TB HP external drive
1 1TB external Fantom drive (which is eSATA)

Based on that, do you still think the Western Digital WD10 EADS-65L5B1 is the Fantom drive(WD), or would it be the Western Digital WD10EAVS-55D7B1?

In any case, I will download the diagnostics and run it.

Thanks again for all your help.

Then it's the eSATA drive, but as the Disks are almost the same WD models the diag is the same.

Thanks. I ran the diagnostic and both discs passed. That was for the Quick Test.

Since everything seems to be working okay now, is there any point to investigate further?

i would run the long test - to be sure about the whole surface

With the utility you should also be able to clear the drive of any data.

rindi, when you say "clear the drive of any data," do you mean -wiping/deleting all the data from  the drive?

nobus, thanks. Will do.

The diagnostic utility should have an option, like zero fill or low level format or something like that, they don't always call it the same. That is the better option than using windows or whatever to delete data.

Since the drive has data in it, I don't want to delete any. So unless I'm misunderstanding what you are suggesting, can you please explain it a different way?

I apologize for the confusion. After trying various things to get rid of the unknown data, I reformatted the drive which basically put me back to square one. I then backed up my current data from the other drives onto the "problematic" drive and after experiencing a few hiccups, everything seemed to work out okay.

I did however just finish the long version of analyzing the disc and it came back with 00 problems on the sectors, so I guess from this point on, the disc seems to be working functionally as well as not finding any errors on it. I appreciate everyone's help in getting to that point. Thank you.