I have a D-Link 624 router which works fine with my WIN 7 PC and my laptop. But, I can't get to the inter net with my Ipad. I also can't access the D-Link as I don't have a password and the original setting doesn't work either.
You need to consult the router's manual (go D-Link support site) for the default password for accessing the D-Link's user interface screens (on the models I've worked on it's User Name: admin Password: admin).
If the password has changed from the default, use the reset to restore defaults.
Connecting via ethernet cable between the laptop and computer will get round the wireless security while you adjust settings. Apart from wireless security type you may need to match the wireless mode to the iPad's.