Freeware: HD Tune
I recently used the great freeware tool HD Tune to diagnose a hard drive problem.
HD Tune - Diagnostic Output
This is the output from the diagnostics I ran on my Toshiba Sat Pro A10 hard disk drive - it confirms that the problems I've been having are due to a serious problem with the drive.
This graph shows that the drive is currently performing as expected but when I tried a more accurate reading, the process halted with a drive read-error.
Shows the features supported by the drive.
HD Tune can read the S.M.A.R.T. statistics that most modern drives can supply. Here, the red highlight indicates a problem with sector relocation - this is a critical attribute.
I initially did a Quick Scan - it detected no problems with the drive.
The regular scan took just under 30 mins for my 30GB drive - so you can expect to wait several hours for a large drive (120GB+). The red squares indicate serious problems with the disk surface. Things can only get worse - better to replace the drive rather than risk losing something important.