Reset button not resetting to factory default

Hi

I have Netgear WNDR4500 v3 router. It was working fine untill I need to changed IPAddress.

But I need to Reset router to factory default setting.

I trued few time pressing Reset button at back of the router with and hold it atleat 10sec.

But It is not resetting to factory default.

Please can some help me.

Thanks

Ish