I'm unsure of the functionality of this trial, but it helped my friend diagnose his computer's slowness and pausing/freezing plus crashes due to a failing hard drive. I use the full version to monitor my drives.http://www.hdsentinel.com/hard_disk_sentinel_trial.php
I really do recommend going into options and finding the setting that replaces your hard drive icons and disabling it.
It could also be memory or even a motherboard issue. But the program will at least help rule out the hard drive or indicate it as the culprit.