This is based solely on my own experiences with other peoples setups and what I've read about Vista Ultimate in particular.
(1) Do not use gparted or any other linux based partition manager to resize the Vista partition. Use the built in Vista utility instead.
(2) Do not allow Linux to install grub into the master boot record. In the Mint install process:
PARTITION > Manual > Step 7 > Advanced > Bootloader you want to put grub into the partition you installed Mint into. For example if WinVista is in sda1 and Mint in in sda2, put Mint's grub into sda2 not in the MBR. You'll then have to install EasyBCD ( http://neosmart.net/dl.php?id=1
) into Vista and use that to setup Vista's native bootloader to boot Mint.
The reason for step 2 has to do with Vista Ultimate in particular. The last service pack when applied to Vista Ultimate makes changes to the MBR itself. If it can't find the Vista MBR the service pack update will fail. Future Service Packs may do the same thing.