i think u need action replay and use regirock regice registeel cheat and then go to snowpint temple and get reggigigas hope this helps
you have to trade from diamond or pearl
the only way you can get regice in heart gold is by trading from Pokemon platinum,diamond and pearl
you can't catch regice in Pokemon diamond, however, with the use of all the regi's traded over you can take them to the temple in snow point city and awaken regigigas
Regice is not obtainable in Pokémon Diamond.Regice isn't in diamond.
The only way to get Regice on pokemon diamond is to transfer them from Ruby, Emerald, or Sapphire.
you cant get it on diamond or pearl!
look for a difrent pokemon
you could only get regice you have to get the skull fossil and if you need the other regis you have to migrate'em or have action replay
you catch one
you have to trade it from a different game, trying ctahing it on Pokemon emerald and migrate it to Pokemon diamond
migrate it from ruby/sapphire.
You can't because regigigas is a 4th gen pokemon. If you want a regigigas then you will have to migrate Regice, registeel and regirock to Diamond, Platinum or pearl