Host: Windows Vista SP2 x64, Intel Xeon X3220 (Quad-Core), 8GB RAM
Guest: Windows 2k Installation with integrated SP4
VBox: 3.0.0 Beta2
I tried to install Windows 2k and it fails after loading all drivers and before you can select the drive/partition. It shows "starting Windows 2000" and dies with 100% CPU-load on one core (VBox-Process takes 25% in Host OS Task-Manager). The problem can be tracked back to IO-APIC support, which is needed for SMP support. Setting it to 1 CPU but leaving IO-APIC on doesn't solve the problem.