Between 2000 and 2006, the Republicans maintained a slight registration advantage over the Democrats.
A 0.15% margin advantage in 2000, a 0.92% margin advantage in 2002, a 0.41% advantage in 2004, and a 0.71% advantage in 2006.
Note: For those "concerned" about "voter fraud" (by which I mean concerned about poor/non-white/young transitory people voting), you have nothing to fear.
It's true that Nevada's Secretary of State, Ross Miller, is a Democrat.
However, he's also been the guy who ordered raiding of ACORN's Las Vegas office, so he's hardly tolerant of fraud.
So, anyway, the Democratic party finally gained a plurality of registered voters in Nevada by October 2007 (0.83%), with many of the new voters registering as Democrats to caucus in January.
As of the closing of the registration books for the 2008 general election, Democrats have an 8.35% margin in registration.