If you're going to reinstall you might consider going in a completely different direction. Don't use a linux grub to boot into Vista - use Vista to boot into a linux grub. The Vista bootloader actually has the capability to boot into linux, it just needs some help. That's where EasyBCD comes in. It can be found here: http://neosmart.net/dl.php?id=1
There's a HowTo based on Ububntu ( same install process as Mint ) here: http://neosmart.net/wiki/display/EBCD/Ubuntu
The trick is how you install Mint. In step 7 of the current version there is an "Advanced" tab that asks where you want to install grub. The default is the MBR. Instead choose the partition where Mint is installed. For example, let's say your partitions are set up as follows:
sda1 - Vista
sda2 - Mint
sda3 - Data
sda4 - swap
When Mint asks you where you want to install grub, answer with sda2. Now boot into Vista, bring up EasyBCD, and point a new entry called "Mint" to sda2. Vista will always be in charge of what boots.
I use a different bootloader because I don't have Vista and the process is the same. I've had multiple Linux OS's on this box all controlled by that bootloader. I have used EasyBCD in setting up other peoples machines and it works very well ( at least I haven't received any complaints ).
Anyway , just something to consider.