I now have WinXP, Windows Vista RC1, and Ubuntu/Kubuntu Linux tri-booting on my laptop. A key to success if you are going to attempt this is the order of installation:

1. Windows XP
2. Windows Vista
3. Linux

If you install Windows Vista first, Windows XP’s boot loader won’t find Vista, and if you try to do a repair on Vista, WinXP won’t be found. There may be a way to fix this, but it’s easier just to install in the order listed above.

When Linux installs grub, at least with Ubuntu, it automatically finds the Vista boot loader. When you select the Vista option from grub, the Vista boot loader should have two options “Run previous version of windows” (i.e. WinXP) or “Run Vista”.

I hope this saves you some time.