http://apcmag.com/turn_one_pc_into_two_for_free.htm

http://www.cublog.cn/u/8754/showart_1978363.html

Software:

       BeTwin 2.00.419 (supports Windows XP SP3)

       (Other similar softwares are : Buddy, HiShare, SoftXpand, Aster XP)

(As for linux platform, you can use Userful Multiplier - Turn 1 linux PC into 10, but it supports only upto Fedora8. I hear that Fedora12 will have a new feature called MultiSeat, which does exactly the same thing, let's open eyes waiting....

http://www.ubuntu-tw.org/modules/newbb/viewtopic.php?topic_id=23284&forum=7&post_id=134576#forumpost134576