The best way to play emulators on the Xbox is to download XBMC-Station.

Extract it typically to E:\EBMC-Emustation.

If you use the Unleash X dashboard by default you will already have a link to run the XBMC-Emustation from the menu. Otherwise just browse using a file browser to E:\XBMC-Emustation\ and launch the default.xbe.

You can manually download the emulators from here and extract each emulators folder contents into each folder in E\XBMC-Emustation\emustation\emulators. However, the simpler way is to use the XBMC Emustation menu (navigate the big menu to XBMC Options) then go to Downloader and in there you can do all the downloads of emulators.

There are some emulators not in the Downloader such as Amiga, which you have to do manually.

Edit the UnleashX config.xml file and add E:\XBMC-Emustation\emustation\emulators to the Emulators menu Paths so it finds them and you don't need them in two places.

If you go into Downloader and it says you have no internet, just come back out and go back in. It seems to do this the first time from a fresh install.

The N64 emulation on Xbox is quite bad. From inside of XBMC-Emustation it flat out doesn't work. From UnleashX it will if you follow the steps below.

Make sure to download Surreal64CE (note the CE at the end) otherwise it doesn't work.

After that, you cannot just use any ROMs, you need to download specifically the Earthworm James N64 ROM set, otherwise they don't work.