According to my experience, dlink default username password should be admin or ADSL if you try not to we can restore the factory set this is the initial password, of course, can also hit 400 customers to ask.
DLink What is the default username password
You can try user name Admin Password Admin or username password is ADSL or root
How to forget the password
1. Hardware Reset:
If you forget the user name or password of the login router configuration interface, you can restore the router to the factory defaults by physical reset, making the login username and password admin and empty. The specific methods for resetting are as follows:
Di-524m live, with a sharp hard object press and hold the power plug next to the reset key about 8 seconds.