http://hddscan.com/
theres a smart extended test takes 30mins to 2hours .
see
S.M.A.R.T. tests
The program allows running three kinds of tests:
Short test – lasts about 1-2 minutes. The test inspects drive’s main schemas, scans small part of drive’s surface and checks sectors from the Pending-list (such sectors may have read errors). This test recommended for quick drive testing.
Extended test – lasts 0.5-2 hours. The test inspects drive’s main schemas and scans the whole drive’s surface.
Conveyance test – usually lasts several minutes. The test inspects drive’s main schemas and logs which may indicate inaccurate transportation or storing.
Copy say ten gig data ,before you begin the test, ,like to partitition a drive into 2 partition,use partition 2 for backups.
CHANCES are drive is ok, drive goes to parking mode when powered off.