First of all i would like to thank you guys so much for all your positive feedback.
The software which emulates another system, the "emulator", is completly legal. Using and downloading the games, called "roms" is legal for certain, old systems like the nes, snes, sega mega drive and things like that. The developers do not own any copyrights because they dont make any money with these systems anymore. Things are getting a bit difficult with systems like the N64 or Gameboy Advance. You are allowed to download a game but you have to erase it in the next 24 hours from your harddisk.
If my page will be accepted here i could simply replace the n64 and gba section with some older systems so there wont be any trouble.