Don't even try downloading an XBOX 360 Emulator they are nothing but Bloatware. They can even infect your computer. You have to complete stupid surveys in order to get their BIOS/ROM. Almost anything with surveys are fake junk. So my advice to you is don't think about downloading any Emulators for PS3 or Xbox 360.
Funny, considering we don't even have a working Xbox emulator yet, and being X86 based, using a modified Windows CE OS, you'd think it would be a heck of a lot easier to emulate then a PPC based platform.
And? Emulators like Dolphin get daily updates, yet there's still a laundry list of things that won't be fixed for years.
So trust the one here who's actually worked on them: Emulation is very, very hard. You aren't going to see a working 360 emulator for at least a decade.