You can use Multilingual Corpus Tool MLCT to do the bach conversion (from UTF16-UTF8 or GBK). Or you can open each file in Word and Save as a plain text file by selecting the designed encoding.
Many thanks, Xiaoz.
I've tried using Word to convert the files but it didn't work.
Could you please provide a new download link to Multilingual Corpus Tool? The one I searched on corpus4u has terminated.
http://www.lancs.ac.uk/staff/piaosl/research/download/download.htm