Microsoft Virtual PC

Microsoft Virtual PC is a virtualization suite for Microsoft Windows operating systems, and an emulation suite for Mac OS X on PowerPC-based systems. The software was originally written by Connectix, and was subsequently acquired by Microsoft. In July 2006 Microsoft released the Windows-hosted version as a free product. In August 2006 Microsoft announced the Macintosh-hosted version would not be ported to Intel-based Macintoshes, effectively discontinuing the product as PowerPC-based Macintoshes are no longer manufactured.

Virtual PC virtualizes/emulates a standard PC and its associated hardware. All Windows operating systems released to date (May, 2008) run on Virtual PC. Other OSes like Linux may run, but are not officialy supported.

Virtual PC emulates the following.
32-bit Intel Pentium II processor (but virtualizes the host processor on Windows versions) with an Intel 440BX chipset
standard SVGA VESA graphics card (S3 Trio 64 PCI with 4 MB Video RAM, adjustable in later versions up to 16 MB)
system BIOS from American Megatrends (AMI) Creative Labs Sound Blaster 16 ISA PnP (native Vista audio when Vista acts as host and guest)[clarify] DEC 21041 (DEC 21140 in newer versions) Ethernet network card.

Not all programs are guaranteed to work because they can use undocumented features of hardware, exotic timings, or unsupported opcodes, although overall compatibility can be considered satisfactory.
The Macintosh version of Virtual PC uses dynamic recompilation to translate the x86 code used by a standard PC into equivalent PowerPC code used by a Mac. The Windows version of Virtual PC also uses dynamic recompilation, but only to translate kernel mode and real mode x86 code into x86 user mode code, while original user mode and virtual 8086 mode code run natively.

It also uses some guest calls traps (especially when using the guest extensions) to accelerate emulation or offer additional features, such as integration with the host environment.

Virtual Hard Disk (VHD) is the file format used by Virtual PC and Virtual Server, for which Microsoft has made available all documentation under the Open Specification Promise.

Supported Host and Guest Operating Systems

 Host Operating Systems

Virtual PC 2007 supports the following as a host operating system (although some, such as Vista Home Premium, will display a warning and work regardless):

Windows Vista ( 32 bit and 64 bit versions of Ultimate, Enterprise, Business editions and European Business N only, not Vista Starter, Vista Home Basic or Vista Home Premium or European Vista Home N editions)
Windows XP ( XP Pro 32 bit and XP x64 64 bit only, not Home or Media Center editions )
Windows Server 2003
Windows Server 2008

Virtual PC 2004 was the last version to support Windows 2000 as the host OS.

Guest Operating Systems

Virtual PC 2007 can use the following as a guest operating system:
Windows Vista (All 32-bit editions)
Windows XP
Windows Server 2008 (Virtual PC 2007 SP1 onwards)
Windows 2000 Professional and Server
Windows 98 Second Edition
Windows Server 2003 Standard Edition
Windows NT 4.0 Server
Certain editions of IBM OS/2

Support for Windows 95, the Windows 98 original release, Windows Me, Windows NT 4.0 Workstation and MS-DOS 6.22 as guest operating systems has been discontinued in VirtualPC 2007. [1]

Guest operating systems which are officially unsupported may be installable, however, they may or may not work properly and Virtual Machine Additions are not available.

Linux guests are officially unsupported in Virtual PC 2004 and 2007 although Virtual Machine Additions support for Linux was available in Connectix's version of Virtual PC before being acquired by Microsoft. Microsoft supports VM Additions for Linux only in their Virtual Server product. Both the OS/2 and Linux VM additions were developed by German company innotek GmbH for Connectix/Microsoft