Although, I don't think anyone actually says "twenty hundred" for the year 2000
People will probably say:
2000: two thousand
2001: two thousand one
2002: two thousand two
2003: two thousand three
2004: two thousand four
2005: two thousand five
2006: two thousand six
2007: two thousand seven
2008: two thousand eight
2009: two thousand nine
2010: twenty ten or two thousand ten
2011: twenty eleven or two thousand eleven
2012: twenty twelve
It's a little awkward to say: twenty oh one or twenty oh two