Configure VirtualBox Windows guest system to use 2 monitors

Purpose

Our host system for VirtualBox is GNU/Linux. We want our guest system, windows, to use two monitors.
This solution should work for all Linux distributions supported by VirtualBox4.

Required software

• Ubuntu 10.10 (aka Maverick) as host for VirtualBox4
• VirtualBox 4
• VirtualBox guest sytem: Windows XP (incl. VirtualBox guest additions)

Configuration

1. Setup virtual guest machine (windows) within vm host system (GNU/Linux) to use two monitors:
   

   Setting up virtualbox 4 to use 2 monitors for windows xp guest

2. Within virtual guest (windows): Configure dual monitor setup:
   

   Setup within virtualbox guest system (windows)

Side note

Upgrading from VirtualBox owned by Sun to VirtualBox owned by Oracle was very smooth. Even for Linux host systems. Oracle, thanks for that!