I am sure the problem either lies in Xp or the Mobo. But it's not really a prob, just an in built limitation, than can be solved with partitioning. (after all, that is why partitioning was invented)
But all attempts at a search on the web result in links to discussion fourums. And the fourum has since moved on, so the link just get me to the same as the 'help room fourum' main page. but the thread 'max hard disk in xp' is no longer on the main page, as it was when the search engine harvested the page.