Windows Vista (final release version) has the following new quirks
1. Vista installer requires that no partition be active (or bootable) on the harddisk! If an active partition is found the Vista installer simply says something like "This Volume is not suitable for installing Windows" and refuses to proceed!!
2. Vista requires that the Windows partition remain active in order to boot.
3. Vista requires that the Vista bootloader be present in the MBR in order to boot. If you put any other bootloader in the MBR (like Grub stage1), Vista will refuse to boot saying that winload.exe is corrupt. This is because Vista's loader checks for a disk signature in the MBR! More info is available here: Vista’s MBR Disk Signature. - Windows BBS. Microsoft talks about it in a whitepaper giving some weird reasons: OEMBoot_Vista - Google Search.
4. The boot.ini file has been replaced by adding yet another entry in the Registry called the Boot Configuration Data with a CLI utility called bcdedit.exe to allow fiddling with the BCD.
To my knowledge the Beta and RC1 versions of Vista did not have restriction #3, but it is present in the final release candidate version.
The Random Bit Bucket