A good HDD diagnostic program

[Michael Alexander]

I have a 2TB Samsung HDD, it's fairly new. ... less than a year, my OS is on it..... recently it has been acting up , with my PC wanting to reboot...... then I get the message that I have to reboot and choose the boot device....

I fiddled with the cable, SATA drive and got the drive back..... runs quietly , but just to make sure, I am looking for a good HDD diagnostic utility.... anyone got a name?

[Mike Stenson (RIP)]

Try this... have not used it myself... 
http://www.sysresccd.org/Main_Page

This might be handy to...
http://www.clonezilla.org/

All the HDD that I have had that did as you describe below/top have eventually failed.
Normally one day after your PC has been off for awhile.
Linux has also been known to read HDD when Windows has given up.
Many Window Technicians carry a Linux rescue disk in their back pockets as a measure of last resort.

Good luck... might be a good idea to get a new....