I have never set up a dual boot system (or used XP much), so can not comment on their quality, but there are links to a few guides here;

[*] http://windows.about.com/cs/dualboot/

[*] http://www.theeldergeek.com/dual_and_multibooting_xp.htm (links to MS' site)

or

Installing(Dual Booting) Windows XP and Win9x Together In One Hard Disk