I have installed 3 os on my system and it does not gives any issue. first i installed xp and then i installed vista, after that i installed fedora 6.

when the system boots i get Grub and it ask's me to choose fedora or others, if i choose others (windows) the system again ask me to choose vista or windows older version, i guess there have to some file like grub.conf in windows where we can make a work around, try to find boot.ini file make a copy it before you make changes or add an operating system there.