We have had this desktop for 4 years and had zero problems with it. I sleep the unit whenever i leave it for an hour or more. But yesterday it shut down completely in sleep process, after returning to it i noticed this. One time upon boot the fan took off like airplane, never heard that before. TechtoolPro4 says "i have 3 bad blocks", and to wipe data and reinstall. Does this seem correct or should i run some other type of diagnostic? Any thoughts much appreciated! Thank you.