jorahan i mean NicHt - not the best of replies there; how about recommending either genuine help, or previous posts that have the answers, or Afterdawn 's search function, maybe then google. And in that order. Otherwise your post serves little or no help
WARNING, These next emulators are not as simple as downloading the file and some ROMS.
Play station: You can download roms for this, Only they should come in an ISO format, Mount it on a Virtual drive with Alcohol 120% or similar. Alternatively you can just buy the cheap PS games and stick them in your DVD drive.
http://www.emulator-zone.com/doc.php/psx/epsxe.html
XBOX: I have yet to meet someone who had this working, You cannot download ROMS or anything. You Must use your XBOX DVD disc and then use the program from the second link to create and .xbe [Xbox Executable] Then you must run the .xbe with the emulator, Very little supported games, I suggest don't even try.
http://www.emulator-zone.com/doc.php/xbox/xeon.html NOTE: I could not find the xbe creator... Search Google to find.