: Downloading ROM files for games you do not physically own is considered a violation of copyright law in many regions.

: Files downloaded from third-party ROM sharing sites or unregulated file hosts frequently carry risks of malware, adware, or executable viruses masked as game files.

If you are looking for information on how to play Pokémon Platinum legally, the safest method is to purchase an original Nintendo DS cartridge and play it on a Nintendo DS/3DS system or dump the ROM directly from your own physical cartridge.