dgm

You do not need an OS selector for two Windows products. I recommend removing
that since it complicates your environment. Get your machine so it boots to
XP without issue as drive C:. Create a second partition wherever you want and
do a fresh install of Vista, but when you install, install to another drive
letter. The drive letters should appear the same during the Vista install.
For instance use C: for XP and D: for Vista. Installing the second operating
system will prevent the first from booting. It will take over the system.
Edit the boot config file on the C: drive by hand so it says what you want.
Make a copy of that file before installing the second OS. Boot to the XP
recover CD, go to recovery console, and issue a FIXBOOT command for the C:
drive. You can then boot to XP again. You can also do trial and error with
the boot config file on the C: drive so a menu is presented allowing you to
choose which OS you want to boot.