I upgraded the xi3650 from vista 32-bit to win7 64-bit. I know you shouldn't do that but hey, I was greedy for better performance.
Can't get hybrid graphics to work, the xi3670 hybrid driver installs, but fujitsu-siemens doesn't offer win7x64 drivers for the 9600M GT card, so in the end it doesn't work.
Others seem to have gotten the 130M card drivers for the xi3670 to work, but those didn't install for me.
I tried some custom nVidia drivers like Dox's, but couldn't get them to work either, and they need ugly hacks like always booting in "ignore driver certificates" mode.
In the end I disabled hybrid graphics from the bios and set the computer to always use the nVidia card. This way I can use nVidia's drivers from their website, which is nice.