I got a nice new Toshiba x205-SLI3 notebook for myself a few weeks back and it of course came pre-loaded with Vista...
After about 8 hours of fiddling with Vista (disabling the annoying security popup, breaking the built-in DRM so I could work on my own videos, and hacking the installer .inf for the latest nVidia drivers so that I could turn on the second video card in the laptop) I finally got it all working... Well, working might not be the correct term - I got Vista to mostly stay out of my way.
This lasted for a few days before Vista popped up and told me that due to excessive hardware changes I had to re-register the OS, so I did. A few days later Vista popped up again and said I'd changed the hardware too much and needed to re-register - this time requiring a phone call to Microsoft.
The third time this happened the person on the other end of the phone accused me of pirating the OS... The OS that came pre-installed from Toshiba...
For the next 12 hours I worked on getting XP onto the laptop - slipstreaming SATA drivers onto a custom XP CD, surgically separating pieces of drivers from other manufacturer's installs, hacking .inf files again, and changing device firmware back to XP compatability... But since then I've not had a single problem with the laptop *and* it runs Horizons like a dream.