Ok. Fixed it.
My fault, as I have redirected "documents" to the wrong place (that's the Vista replacement for "my documents". ShipSim2008 needs it for the userdata files etc. Without that information, it waits with a blue window.
I haven't had a dual-boot since 98/XP in 2003, Vista needs 3rd-party software to DB right?
No, so long as you install to another folder or drive, it handles it for you, quite well. There isn't a "boot.ini" file any more, but you just change the setttings from "System Properties" dialogue.
I am going to get another machine to sextuple boot, with Windows 95, 98SE, ME, Win2K, XP and Vista. That just leaves NT4 and Home Server to go. But I have those running on other machines here.