No Dave.
If you put XP's bootloader back, it will just be replaced by Vista's again as soon as you install Vista.
As long as you own Vista, there's no reason not to use its bootmgr even just for booting XP.
(a lot of people come here to ask if they can do just that, to be able to use EasyBCD to manage the boot)
The previous instructions I gave would have left the spurious Vista entry in place, but you just wouldn't have seen the boot menu at startup because of the zero timeout.
If you intend to reinstall Vista, a better approach would be to leave the timeout at non zero, but remove the "busted" Vista entry with EasyBCD add/remove entries.
When you install the new Vista, it will see the existing BCD, add itself as a new entry and your dual boot will be up and running as soon as the Vista install completes.
Your BCD will be on the non-Vista disk, but that's not a problem unless you want to get rid of that original disk in the future.
If you'd prefer the Vista disk to contain the BCD and control the boot, you'll need to make it the 1st in your BIOS boot sequence, disconnect the old one temporarily, and do a clean install of Vista on the virgin HDD.
Then follow the advice in the
sticky thread to get your dual boot back after you reconnect the old disk with it 2nd in the BIOS.