SpinRite is at best useless, and at worst a drive killer. Data recovery professionals will tell you that it potentially accelerates the failure of weak heads.
If you examine the screenshots at grc.com, you will find that the most recent example is for a 200MB model (MEGAbytes, not GIGAbytes).
Try a comprehensive SMART diagnostic. Look for reallocated, pending, or uncorrectable sectors.
HD Sentinel (DOS / Windows / Linux): http://www.hdsentinel.com/
HDDScan for Windows: http://hddscan.com/
See this article for SMART info: http://en.wikipedia.org/wiki/S.M.A.R.T.