Your definitely on the right track. This could happen in two different ways, either they submitted both versions of the same url (like you suggested), or sites are linking to him using different versions of the same url, (and the spider crawls these links indexing the same page 2 different ways).

This probably isn't a good method to follow if your looking to get longevity out of your listings. Alta Vista does have duplicate detection methods, and it's usually just a matter of time before one of the listings is dropped.

Thanks I guess i won't be doing that than. Well, their duplications methods have not been catching my competitors lately, but i guess i will talk to altavista again. One of my competitor has five domains and all of five of them are EXACTLY alike. It has been about two weeks since i email altavista and they haven't done anything to thier sites, yet. My competitor has about five sites in the top 20... :( For now, all i can do is wait and try to get more links pointing to my site - how fun!!!! :)

You should also really work on the content of your site to make sure that your chosen keywords are used on almost every page of your site (if not on every page). This act of making your site "themed" should get you better results on term vector databases (such as AV) than just simply optaining links. (don't get me wrong, relevant links are great, but it will take you much longer to obtain enough links to get a noticable boost)

While you can see the "competitor's" record in the database, use the opportunity to analyse why he's got #1, compared to your page. Once you've tried to identify the reasons, don't "copy" what they've done, as Sethe says, work on your site to improve it.