Hard Disk Monitoring

Hello Friends,

I am going to buy a 2nd hand hard drive. Any suggestion how can I check the condition of the hard disk? How many days it has been used? Please help..

Please check Support -> Frequently Asked Questions page:
https://www.hdsentinel.com/faq.php

There are different sections:

How to start using Hard Disk Sentinel?
https://www.hdsentinel.com/faq_how_to_start.php

which shows generally how to use start using: the Overview page immediately shows the power on time value (how much days/hours used. Please note days mean 24 hours of usage in this area). And

Hard disk health is low or recently changed or I just installed a new (used) hard disk. How can I perform a deep analysis?
https://www.hdsentinel.com/faq.php#tests

which shows the recommended steps to perform on a new (or used) hard disk drive, before using it for actual storage, exactly to verify the status: reveal any possible issues - or confirm if the disk drive is working correctly.