M$xp would have to be the easiest M$ O/S to dual / triple with.
- just pop that newly burnt cd into the cd-drive & shutdown / restart your desktop !.
if it's set to boot from the cd, 1st, the just click on the install icon on the linux desktop.
go with the option the share the hdd with the existing O/S ( M$).
use all the default(s) that appear during the install.
If you go with Mint as the linux O/S, use mint 7.