Windows Vista Help Pages
GRUB can no longer boot the release version of Windows Vista, Unless a Unique Identifier is keept in the MBR.
Idea: 
I was thinking that a option in Anaconda that reads "Windows Vista System" so Anaconda can install GRUB in a way that does not stop Vista from booting?
- Anaconda could dd out the unique identifier from the MBR and then let GRUB install its self then reinsert the UUID?
Be warned if you are planning on doing a dual boot
It is recommended to use these steps to backup your MBR untill more is known!
Steps
[ PAGE to be UPDATED ] Very Soon!
Before you install bring up a Live CD/DVD and mount a USB pen, for example:
$su -
Now make a copy of your MBR to it like so:
Where /dev/sda is your HDD. N.B. This also makes a backup of your partition table as that is stored in the MBR, if you just what to copy th boot loader code then use:
bs=443
GRUB
rootnoverify(hd0,x) chainloader +1 boot
No longer works.
Common Errors that are Displayed
The file /Windows/system32/winload.exe can not be found or is corrupt.
- This means that windows can not find its own boot loader in the MBR, it must now do some kind of sum check ?
Other unknown issues more to be added...