Test both drives - the internal one with the Dell diagnostics (F12 at boot) and the external with its manufacturer's test utility.

Can't use and understand the utility soft, 'coz it's japanese. any other soft to test? I used Paragon Partution manager to tormat and and windows, both same result.

Most drive manufacturers have their own test software. Determine the manufacturer of the drives are download the utility to test the drive from the manufacturer.

Yep I know, I'm here in Japan working and I bought it here. I visited their website but it's all writen in Japanese no English.