VMWare hosts each guest operating system in a separate, secure virtual machine. Each virtual machine (VM) has its own virtual CPU, memory, disk, etc. and all of the virtual hardware is mapped to your computer's real hardware. Each virtual machine also comes complete with its own BIOS that can be edited the same way you'd edit the real BIOS on the computer that VMWare is running on. This lets you customize your virtual machines and control all of the usual stuff that you can control via your PC's actual BIOS. Since each operating system runs in its own virtual machine, none of them should adversely affect the other. You can install whatever applications you want and it doesn't matter if they are all completely unstable. They can't affect your other guest operating systems nor can they affect your host operating system. Even viruses running in the guest operating system can't do any damage to other guest operating systems or to the host operating system. This makes VMWare a great tool for anyone that needs to test applications, do development work or just generally muck around with things in a safe environment. However, the overhead of each VM will eat into the CPU cycles available to other running VMs and any other Windows applications you have open. Be aware though that you will need approximately the same amount of disk space to install an operating system running in a virtual machine as you would if you installed it regularly on a separate PC. So plan ahead and bear in mind the size of your actual hard disk before you decide what other operating system you want to install and which applications you want to install with them. And, speaking of testing, VMWare also lets you take a "snapshot" of your virtual machine whenever you want. This means that you can roll back any changes to your virtual machine with just a click, like a Windows Restore Point. For software developers or reviewers like us, this is an incredibly handy tool that can be a real time saver when dealing with multiple operating systems.
