Ticket #15129 (closed defect: fixed) OpenGL doesn't work in Windows 2000 (Quake 3 Arena fails to start) “The Unofficial Update Rollup for Windows 2000 seems to fix this error.”

In VirtualBox 4.2.26 make the following changes to the settings of the VM:

1. Settings → System → Processor tab → Uncheck “Enable PAE/NX”.
2. Settings → System → Acceleration tab → Uncheck “Enable VT-x/AMD-V”.

This is to prevent the “Fault outside of MS-DOS Extender.” error during Windows 98 setup.
Source: VirtualBox forums - [Solved] Fault outside of MS-DOS Extender (win98 install)

See also:
VirtualBox forums - Windows 98SE step by step
VirtualBox forums - Tutorial: Windows 95/98 guest OSes
VirtualBox forums - Win98SE with ACPI - Success At Last!
Using above forum posts on VirtualBox 4.3.16 with a Windows 98 FE Dutch CD did not produce a stable installation of Windows 98.

“PXE does work IF it's one of the AMD adapters AND you bridge the VM adapter to a host adapter. Same errors as before if you don't bridge. The Intel adapter still won't even try PXE (…).”
Source: Akita on VirtualBox on Windows Hosts forum - Cannot PXE Boot (network boot) with Host IF Networking. Tested with VirtualBox 2.2.2.