More accidentally I found Sun´s Virtual Box – which is free and open source. It´s small, fast, reliable, supports x64 virtual systems on a 32bit machine, runs on several plattforms (win, mac, linux, open solaris) and is very advanced in it´s functionality.
And did I mention that it´s free ?
I´m using it with a Windows 7 x64, a Windows XP x64 and a Windows XP 32bit installation and in all 3 environments it runs great. For windows users it provides a nice graphical user interface.
It supports USB, LAN and IDE / SATA sharing – the guest with the host machine and a possibility to pass-through the devices directly to the virtual machine. Furthermore you can mount iso´s directly into the virtual machine and use them as boot device or simply as CD-drive.
The only thing I miss is a good Direct 3D integration. Though there is an (experimental) support for D3D, it doesn´t work to good practically. I tested it with some older games and most of them fail to recognize the virtual graphics adapter as a real D3D compatible graphic card. This is kinda sad, cause it would have been an easy possibility to enjoy older games in a Windows XP or a MSDOS virtual machine.
But as final conclusion – if you need a free, reliable and fast virtualization software, Sun´s Virtual Box is your pick.