facti.net

There is a good guide for the conversion of VMware virtual images to VirtualBox vdi files. Theoretically, this should result in machines created using VMware working under VirtualBox. Be forewarned that while the process works (a .vdi is created and appears to be fine) the machine that is created will not actually work, at least under some circumstances (such as my test case using a Windows XP image) since there are incompatibilities in the agp440.sys that prevent the newly created VirtualBox image from actually booting. There is a method to fix the borked virtual machine I have not yet tried but will do so when time permits.

Apart from the conversion problem my simple tests with VirtualBox worked reasonably well.
Creating a Fedora 8 virtual system worked, and running VirtualBox
alongside VMware works ok as can be seen from the screenshot.