Actually making a Google search of "Software Raid XP" or similar search brings back ton's of websites/forumns discussing this with 2000 and XP. I think for a file/data server it would work fairly well. I think a controller based setup would work better for larger network or application based servers. Otherwise you would get lots of CPU utilization and it would slow down. For data storage for HTPC of movies/songs/etc... I'll have to check out motherboards and hard drives to see what it would cost to achieve this type of setup...
