List with best Virtual PC Software :

1. VMware
   VMware provides virtual machines for x86 that can run unmodified PC operating systems. The technology involved in doing this is complex and also incurs (sometimes significant) performance overheads with hosted VMware products (VM Server and Workstation).
2. Xen
   Xen Virtualization system whose motivation differs from that of Denali in that it is intended to run a moderate number of full-featured operating systems, rather than a large number of specialised, lightweight ones (Denali\’s virtual machines support specialised minimal OSs for Internet services.
3. Virtual PC
   Virtual PC is a powerful software virtualization solution that allows you to run multiple PC-based operating systems simultaneously on one workstation, providing a safety net to maintain compatibility with legacy applications while you migrate to a new operating system.
4. Parallels / Virtuozzo
   Parallels provides virtualization of x86 for running unmodified PC operating systems. It also uses a lightweight hypervisor technology in order to improve security and to increase the efficiency. Parallels has become popular for its ability to run Windows as a guest under Mac OS X on the Apple-Intel architecture. Virtuozzo replaces the hardware abstraction layer with a modified version enabling it to run with better performance of the OS, but forces all the VMs on a hardware box to all run the same OS, with some flexibility to support various Linux distributions on the same server.
5. QEMU
   QEMU is a simulator based on a virtual machine, which gives it the ability to emulate a variety of guest CPU architectures on many different host platforms.
6. VirtualBox
   VirtualBox is an open source (GPL)/proprietary virtual machine developed by Sun Microsystems. It allows virtualization of x86 and supports various host operating systems including Windows, Linux, BSD and Solaris. It also supports VMware Workstation Virtual Machine Disk Format.
7. Virtual Iron
   Virtual Iron provides virtual machines for x86 that run unmodified operating systems, such as Windows, Red Hat and SUSE.