Syslinux - Mar 2005 - about making syslinux boot from hard disk drive question

Dear Sir
 
As I follow the procedure described in the web site to install syslinux to
my DOS hard disk drive,
 
but the return code is ERROR 440D: Unable to lock drive for exclusive access
 
and I issue command lock c: as web site for Win95/98/ME DOS box situation
then try it again but it failed again.
 
Is there anyone can tell me what's wrong I encountered ?
 
Best Regards
 
Steven W Yang