VirtualBox is a free software virtual machine system by Innotek, who are now part of Sun.

Be careful of reporting bugs found in Wine running in a VirtualBox instance of an operating system - it's good at supported guests (Windows, Linux and Solaris) but not others. e.g. X11 won't start on OpenBSD in VirtualBox - the VirtualBox developers acknowledge it's their bug, but won't fix it because isn't affecting paying customers, so don't bother asking unless you have a large Sun contract.

So you may wish to use a VM only for investigation - only file bugs that manifest on an OS installed directly to a physical PC.

Other VMs are more robust emulations, e.g. OpenBSD works on Qemu on Linux (if you're not using kqemu).