General LadyEye gave you the link you asked for (to find past owners and site versions associated with domain names) .......
but in answering the question in the title of your thread,
if you find someone using a domain name that is the same as or similar to your business and you feel that you have provable "first use" of it (find this by using WHOIS to see date created),
or that their use infringes on your business in any way, you have the right to petition ICANN for remedy (which may result in the domain name being transferred to you outright, taken off the market, or other actions). Some excerpts below illustrate this:
3. The Complaint (a) Any person or entity may initiate an administrative proceeding by submitting a complaint in accordance with the Policy and these Rules to any Provider approved by ICANN. (vi) Specify the domain name(s) that is/are the subject of the complaint; (vii) Identify the Registrar(s) with whom the domain name(s) is/are registered at the time the complaint is filed; (viii) Specify the trademark(s) or service mark(s) on which the complaint is based and, for each mark, describe the goods or services, if any, with which the mark is used (Complainant may also separately describe other goods and services with which it intends, at the time the complaint is submitted, to use the mark in the future.); (ix) Describe, in accordance with the Policy, the grounds on which the complaint is made including, in particular,(1) the manner in which the domain name(s) is/are identical or confusingly similar to a trademark or service mark in which the Complainant has rights; and
(2) why the Respondent (domain-name holder) should be considered as having no rights or legitimate interests in respect of the domain name(s) that is/are the subject of the complaint; and
(3) why the domain name(s) should be considered as having been registered and being used in bad faith (The description should, for elements (2) and (3), discuss any aspects of Paragraphs 4(b) and 4(c)of the Policy that are applicable. The description shall comply with any word or page limit set forth in the Provider's Supplemental Rules.);
(x) Specify, in accordance with the Policy, the remedies sought;
You may find the whole ICANN Policy regarding Domain Name Disputes here >>
http://www.icann.org/en/dndr/udrp/uniform-rules.htm 
02-22-2009, 10:16 PM
What happens if you find company using your domain name? 
Re: What happens if you find company using your domaion name? 
