It looks like your parents have an old HDD. I'd watch for failures, and absolutely would back it up NOW. But it doesn't need to be replaced unless the freezing is intollerable. If it is a real concern than you need to replace the HDD.
Thanks for the response. The computer is quite old; about 8 years I'd say, though the HD is only about 4. I had been planning on doing a reformat, but seeing as how the HD is dying, I'll wait and get a new HD first.