Vista in VirtualBox on RedHat 4
I was able to install Vista on Linux RedHat 4 with VirtualBox, on an X4100.
The first attempt failed with the following error:
The VirtualBox support driver which is running is from a different version of VirtualBox.
You can correct this by stopping all running instances of VirtualBox and reinstalling the software..
A Google search proved that I was using the 32 bit VirtualBox rpm, where I should be using the 64 bits one. Alas, no 64 bit rpm for RedHat 4. I tried the RedHat 5 version, but it failed the pre-install dependancy checking. So I used the integrated installer (VirtualBox_1.5.4_Linux_amd64.run), ran it, and it worked.
One trick: By default, the VirtualBox GUI uses the "Right Ctl" key as a magic key to release the keyboard and mouse grab. Unfortunatelly, on my Sun keyboard, there is no right ctrl key... I had to shutdown the Vista VM, access the VirtualBox config menu, and change the Hot Key to Left Ctl 
