You could download and install the
Western Digital Data Lifeguard Diagnostic tool to test the 500GB hard drive. Then connect the powered 500GB hard drive to your computer's USB port.
Do not let the computer format the drive. Run DLG and agree to the terms. DLG will scan your system and the 500GB hard drive should appear.
From the top window select the 500GB hard drive and right above the window click the little hard drive icon to open the options window. Start by selecting the "Quick Test" option. If the hard drive passes the self-test then it is likely okay. Sometimes this is good enough to determine whether the hard drive is failing, also saves a lot of time. If you want to be absolutely certain that the hard drive is okay, next select the "Extended Test" option. This test will scan the entire surface of the hard drive looking for bad sectors. While this test is much more thorough, depending on the size of the hard drive, this test can take a very long time to complete. Whatever you do, do not select "Write Zeros" as that will wipe the drive. Both the Quick and Extended tests
should be non-destructive, but I won't guarantee that will always be the case. When in doubt, make a backup.
You can also see the hard drive's S.M.A.R.T. values, but in my experience those values are almost useless to the average user and depending on the manufacture, reporting varies.
Before beginning, read the DLG instructions beneath the download link.