Windows XP and the Microsoft Virtual Machine
Early versions of Windows XP (and indeed previous versions of Microsoft's Operating Systems) shipped with the Microsoft Virtual Machine. However, In early 2003, Microsoft lost a legal case against Sun (the people who make Java) and had to stop including the Microsoft Virtual Machine (MSVM) with Windows XP. This means anyone buying a new PC or upgrading their operating system to Windows XP now will not get the MSVM any more. However, it may be that some PC manufacturers will be including Sun's own version of the Virtual Machine on new PC's.