
VMware is the best, but it just doesn't have the enough graphical power to support Unity (or most any graphical app). A key emphasis is on security by using as small a code base as possible, making it not just secure but especially flexible. I have been using VMware (for Windows) and VMware Fusion (for Mac) daily for the last three years in my day-job and have played with Parallels and MS Virtual PC. The service is especially applicable for hyperscale clouds, and can easily be used with AWS, Azure, Rackspace, IBM Softlayer, and Oracle. The Xen Project software is even being used in automotive and aviation systems.

This includes but is not restricted to Infrastructure as a Service (IaaS) applications, desktop virtualization, and security virtualized. It is especially used for advanced virtualization, not least for servers, in both commercial and open source environments. Once VMware Tools is installed, click on VM drop down menu on the Windows XP Mode VM window, and click on Enter Unity to enable seamless applications publishing from Windows XP Mode to Windows 7 host. The Xen Project now works with The Linux Foundation in promoting open source applications.
BEST VM PROGRAM FOR UNITY XP PRO
A Commercial License can be applied to enable Workstation Player to run Restricted Virtual Machines created by VMware Workstation Pro and Fusion Pro.
BEST VM PROGRAM FOR UNITY XP FOR FREE
Originally developed by Cambridge University, the staff who created it spun it into a company that was later acquired by Citrix. VMware Workstation Player (formerly known as Player Pro) is a desktop hypervisor application that delivers local virtualization features and is available for free for personal use. This is great because it hides the XP desktop and makes Visual Studio appear to be just another OS X program. I keep the Unity project in a folder on the OS X desktop and then open the solution from inside XP.

Xen Project is a free and open source virtual machine monitor (VMM), intended to serve as a type-1 hyperviser for multiple operating systems using the same hardware. Doing this allows very easy file sharing between OS X and XP.
