a stock 07 E90 would have halogens, an e92 (any trim level) will have xenons.
for the 07 E90, you can tell if it has xenons if it has the corona rings (angel eyes / halos). if it doesnt have corona rings, it is halogen headlights.
Current: 2011 Mini Cooper R56 MT 'Justa'
Previous BMWs: 2008 E92 328i MT Sport / 2005 E83 X3 2.5i