Here is a link [1] to a site demonstrating how to do a clean install of Windows Vista without having to install Windows XP first.
It isn't the easiest process, but if you are confident enough and can follow the instructions, it should be a do-it-yourself project.
Links:
[1] http://www.dailytech.com/article.aspx?newsid=5932
[2] https://www.paypal.com/cgi-bin/webscr?cmd=_xclick&business=rick@yourpcpartner.com&item_name=Buy
[3] http://www.helpmerick.com/node/1260
[4] http://www.helpmerick.com/node/204