1) since marriage has solemnised as per hindu rituals it is valid marriage .
2) the marriage is not null and void on grounds that marriage is not registered .
3) if for 2 years husband and wife are staying separate file for divorce by mutual consent .
4) if one of the parties refuse consent then file for contested divorce on grounds of mental cruelty , desertion .
5) you cannot remarry during subsistence of earlier marriage
6) if you remarry during subsistence of earlier marriage your wife can file case of bigamy against you .
7) best option is to obtain divorce by mutual consent . it takes around 6 months