Sanatha Dharma is a path so broad, all encompassing, that gathers all human possibilities and their possible symbols towards a transcendental and objective reality.
However, in a historical conception, Hinduism can't be understood outside the society it emerged from, in the sense that its recognition needed both an identity, linked to ethnicity, as Indians, as well as a classification of functions inside such system, as castes.
Being the sensible religion that it is, it is natural that many westerner feel attracted to Hinduism. The opinions regarding conversion are diverse, it depends on the particular orientation or sect of Hinduism the adherent wishes to ascribe to, through certain mechanisms and interpretation of rules like varna (duty, task, function, job) as a describer of caste. There are modern forms of Hinduism as the Arya Samaj or the Brahmo Samaj which are reformed forms of Hinduism, which are open to receive foreigners, but whose authority as legit forms of Hinduism is questioned by orthodoxy. So, there are other Hindu teachers that advice to keep with one's original religion (Christianity as the Hinduism of westerns), while studying Hinduism as further knowledge.
I'm not very sure about the full validity of the next, but it is a great reading if you are interested in officially converting to Hinduism:How to become a Hindu