Its not live tv but you can download addon's for XBMC that will let you stream almost any show through XBMC, including many movies in HD.
The first addon is called 1Channel. It is the best for tv show's as it group's them by series, then season's and finally by episodes.
The second is called Icefilms. It has a large selection of HD movies and many more available to stream right to your computer instantly, it also does many tv show's but the organization is not nearly as good as 1Channel.