There is also a Universal Boot Loader by that name that will see a push button type gui for choosing any OS you install into the mbr. But with two copies of Windows the boot,ini is the ticket where a simple trip into the msconfig or NotePad solves everything once one has added the other into it's own after first "detecting it" the way Windows itself works.
For Grub you still have to edit the bootmenu.lst file in order to dual boot Windows with a distro. That's how Grub works with Windows that way. When dual booting two Windows installations the last one generally the newer version of Windows goes on last and then adds the other into it's own boot loader upon detection as a boot option.
My last build here saw XP Home, Pro, and Vista Home Premuim mutlibooted there with the Home version on the first of two ide drives,, Vista on the second, and Pro on the first of two sata models. Vista had to reinstalled a few times there to see both versions of XP added in with Pro set as the default. Prior ro Vista XP Pro was on the second ide and configured strictly through a manual edit of the boot.ini file.