Are right handed neutrinos actually antineutrinos and vice versa? Is it experimentally ruled out that right-handed neutrinos are actually antineutrinos, and left-handed antineutrinos are neutrinos ?
 A: Short answer: Unknown
Slightly longer answer: the situation you describer would obtain if neutrinos were Majorana particles (and thus not Dirac particles). It is favored by theorists because it feeds into a nice explanation of why the neutrinos are so light by comparison to the other massive particles.
Experiments are underway that might settle the question by detecting so called "neutrino-less double beta decay" reactions which are forbidden for Dirac neutrinos but allowed for Majorana neutrinos. 
June 2012: One of the neutrino-less double beta decay experiments, EXO, has announced modestly significant limit on the possible masses of the neutrinos if they are Majorana particles. This limit excludes some of the theoretically favored scenarios. Right now the significance is too low for a lot of fanfare, but this might be a the first indication of a surprise.
January 2013: KamLAND-Zen has reported a slight improvement on the EXO result as of the end of their first run, with purification of the working material planned before resuming data taking.
July 2013: EXO released another paper last month, setting a much beter measurement of the decay with neutrinos:
$$ T_{1/2}^{2\nu\beta\beta} = \left( 2.172 \pm 0.017\text{(stat)}\pm 0.060\text{(sys)} \right) \times 10^{21} \text{ years}\,,$$
but they do not update their limit for neutrino-less double beta decay, so still no definitive answer on Majorana/Dirac.
August 2013: GERDA has published a report on a low significance null result in the July 17 issue of Phys. Rev. Lett. (also as arXive:1307.4720). Like the EXO and KamnLAND-ZEN results this isn't a strong result by itself, but the combination of all three is starting to look pretty significant.
