In order to recover the files on the USB harddisk, I bought a 2TB harddisk for recovery. In future, I would have to keep buying large harddisk.
Part of my data was recovered using Get Data Back NTFS on Hiren BootCD 10.6 before the harddisk became inaccessible. Even trying to format the harddisk failed. It took me more than one week of trying before I decided to give up.
As the harddisk was purchased less than a year, it should be under warranty but the sales receipt could not be found to show to the service centre. However, since the warranty was for 3 years, the service centre would arrange for one to one exchange if it was prove to be faulty.
So I took a long bus ride to the service centre, I was told that as there was no stock and it would take about a month, I could upgrade to a new USB 3.0 model with the same capacity by paying S$21.40.
I was caught unexpected with such an option and such situation, unwilling to travel all the way back to the service centre again, I agreed to pay S$21.40 to have the harddisk upgraded to USB 3.0 version with the warranty covered since the initial date of purchase.
The new USB 3.0 harddisk is bundled with NTI Backup Now EZ software which would perform backup of files and even the whole computer on schedule. In the past, I have never bothered to install and look at the software bundled with the external USB harddisk I purchased. However due to the recent events, I installed and try out the software. It is a good bundle as otherwise users would be unlikely to purchase backup software.
It is better not to put all your data onto a single large harddisk but a few so that it would not take too long for recovery and also spread the risk of harddisk failure. Also use 2.5" USB harddisk only for portable storage instead of having it connected to personal computer over long period of time. For external storage, use 3.5" harddisk with fan.