One of my favorite uses of Virtual PC / Virtual Server is to play around with various different operating systems. The Amiga research operating system (AROS) is one that caught my eye – downloadable from http://www.aros.org/ the developers describe it as follows:
AROS is a portable and free desktop operating system aiming at being compatible with AmigaOS 3.1, while improving on it in many areas. The source code is available under an open source license, which allows anyone to freely improve upon it.
AROS does not support installation to a hard disk at this stage – but they do provide a bootable CD that works well under Virtual PC. One interesting thing that I found is that when running AROS under Virtual PC there is a periodic pause in the mouse movement, however this problem does not happen when running AROS under Virtual Server: