While Emulators aren't illegal, ROMs are VERY illegal if you don't already own the cartridge or CD/DVD of the game. According to copyright laws though, you can legally own ROMs only if used as a backup copy of the game you already have. Anymore than one copy though would make if illegal because that would count as piracy. Owning the ROM without having the game is obvious piracy since you didn't pay a single dime to have the game in the first place. So, in conclusion, only download a ROM of a game if you already have the game and just want to have the ROM as a backup or as an alternate way of playing the game on another platform (such as your computer). Otherwise, it's consider warez.
Also, I believe ISOs is also under the same rules as ROMs so be aware of that too when handling ISOs.
-- SavageX
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"...and if you don't like that, then you need to be slugged in the face repeatedly, until my hands are soaked in blood. Have a nice day!"
http://www.savagex.net
The cake is a lie... THE CAKE IS A LIE!!!!!