Nope, if its necessary to fix its as simple as installing EasyBCD in Vista after install and adding the missing XP/Windows 7 entries.
Actually, it depends on which partition is labeled as "system" in Disk Management. If this is Vista's partition, reinstalling Vista (assuming at least, if you reformat the partition first) to it will make the boot files go "bye-bye", rendering your other OSes unbootable until you reinstall Vista, and use EasyBCD 2.0 Beta to re-add the XP and Win 7 entries to the boot menu.