Do you have S.M.A.R.T. enabled in BIOS? If so, you'll probably get errors messages during boot up. Have to admit S.M.A.R.T. doesn't always work...
When the program freezes during HD read/write, are they always accessing a certain file? If so, there's a high probability that it's really a HD problem. Sadly, I was unfortunate enough to experience that several times in the past
Also, look for ticking sound or HD resetting sound, they're signs of problem HD.
HD will die sooner or later, it's just matter of when.