Then I guess your HDD has some bad sectors related problem. I would advise you to back up the data that is stored on it as soon as possible.
In case the drive is still under warranty, you can call WD's Support either by phone or e-mail and eventually RMA the drive.
You can test the drive with WD's Data Lifeguard Diagnostic tool. The results will show whether there is something wrong with the drive. In case there is something wrong with it, you need to back up the data stored on it as soon as possible
Apart from that, as many Windows 8 users are facing 100% Disk Usage issue, you can try disabling several Windows Services like: Superfetch, Windows Search and BITS. Check this thread out: http://www.tomshardware.co.uk/answers/id-2027511/windows-disk-usage-100-problem.html
I have disable those services way back cause i have an ssd for a boot drive.
Now with DLG tool, it says my drive is ok but when i do the extended test it hangs up and i have to restart my pc and when i took a look at the smart it says that the hard drive has current pending sectors
Then I guess your HDD has some bad sectors related problem. I would advise you to back up the data that is stored on it as soon as possible.
In case the drive is still under warranty, you can call WD's Support either by phone or e-mail and eventually RMA the drive.