problem getting to run pokemon diamond...HELP!!

I downloded a NDS Emulator exclusivly for pokemon diamond. In the past i have been ver good at working with emulators and have had no problems at all. However, when i tried to play pokemon diamond (which i downloaded from this site) on the no$gba emulator i downloaded the emulator said i had a bad header checksum, a bad ROM entry piont at header [0002], and a bad fixed value 96h at header [0B2h]. Did i download a corrupt ROM? I also seem to have a problem with the emulator saying my downloaded ROM is not a nds file....HELP!!

You have to extract the rom from the archive. Look in the Tutorials section for the appropriate tutorial. If you downloaded Pokemon Diamond from RomUlation, it's not the ROM that's bad. If you have extracted it, and you got a .nds file, on which you dragged onto no$gba etc. redownload it.