As suggested, I have downloaded Seatools. It has detected Toshiba harddrives. Though there is only one drive, it has detected as two drives with same serials. Is it due to two partitions?
Yes, I think so.
I ran short DST and it passes. Tried Long DST many times. I couldn't complete it yet. The system crashes even before it finishes. One day with minimum programs open, it ran about 3 hours and a half and reached almost 80% and the box crashed. I think I will have to get a new drive and check. Any other suggestion?
That does sound very suspicious.
If you want to be sure, run the SeaTools from a bootable USB - simply pick the SeaTools for DOS
on the download page, copy the exe to a USB stick and change the boot order in your BIOS to boot from USB (most modern laptops have this capability)
Then when you run the test if it gets to a broken part of the drive it will not crash as it is running from the USB stick not the broken hard drive and you should get some results.