I have attempted to follow dual boot guides found everywhere, but none tailor specifically to (or eve mention) Vista. This is a problem, because Vista does not use the same method of boot as previous versions of NT.
So far, in my many failed attempts at creating a Vista dual boot, I have experienced this:
When I install Solaris 10 on any partition (Solaris installs correctly and works great), and then attempt to install Windows Vista, Vista says all of my partitions do not meet its requirements for installation (that the drive is NTFS and at least 12 GB is all it tells me). Even after formatting, deleting, recreating, and reformatting a drive, the drive is still unusable. Only after deleting ALL drives, including Solaris 10, and recreating and brand new first partition does Vista allow me to install. If I create a partition that Vista allows me to use, and also a partition to use with Solaris, and THEN install Solaris, the partition that Vista liked can no longer be used!
When I install Windows Vista first (and it works fine) (which is what I tried first and reasoned is what I should be doing), and then install Solaris 10 on a partition (it installs correctlt and works great), I load up my computer and go into the GRUB bootloader. I can select Windows. However, when attempting to load windows, I get an error (in the Vista font by the way) that says my operating system cannot be loaded. When I load my Vista install disc, it cannot find any installations of windows, and it cannot repair the master boot record, saying something like the filesystem is corrupt. However, just as an experiment, I loaded Vista onto the former Solaris drive, and looked at my first partition. Every file was there, intact.
I have attempted this with Windows Home Premium 32 bit, Windows Business 32 bit, and Vista Ultimate x64. I don't want to believe that it's impossible to load Vista and Solaris simultaneously, I've seen as much stating its impossibility as I've seen documents telling me how to do it (<- cold irony).
As long as I can get AN INSTALLATION of Solaris 10 on my machine at the same time I have Vista able to boot, I'm fine, but I seem to have lost on all fronts.