Can't uncompress certain games.

When I download certain roms, and try to uncompress them, I can't. 7-zip tells me that the file is broken. WinZip said it failed too. This does not happen for all the games, but it has happened for all the DS games I downloaded. I noticed a possible correlation to the ones that seem to come form other hosts than romulaiton. I tried pokemon platinum and animal crossing - wild world, for example, and neither was able to unpack. Help please!

First download Winrar like Raysie said
Then in that doesn't work try to download a file again.

Download WinRAR!http://www.rarlab.com/download.htmOnce installed. Just right-click the downloaded files and click "Extract Files". You should have your .nds game now.