I have win98 dual booting XP, DOS 6 and ME installed on Virtual Machines. The main requirement is haveing enough memory so that they can run smoothly. I have not, repeat NOT had a problem with my main Operating System when installing Virtual Machines. You are only installing to the Virtual environment not overwriting your Operating System.
Virtual PC lets you create one or more virtual machines, each running its own operating system, on a single physical computer. The virtual machine emulates a standard x86-based computer, including all the basic hardware components except the processor. By using emulated hardware and the processor in the physical computer, each virtual machine works like a separate physical computer. Because each virtual machine has its own operating system, you can run several different operating systems at the same time on a single computer.