Originally Posted by Noodle Wazlib
virtual machine, so you could run a program like virtual box (which is free and excellent and free) and boot another OS inside of your running OS
dual booting was probably more of a necessity back when there were not dual- to quad-core CPUs and low available system memory. Now that most folks are on 2-4 CPU cores and 8+ gb of RAM, you can pretty easily run at least 1 VM on a standard computer.
My gaming rig has no problem running a host OS, and 3 additional VMs all at the same time. Rarely something I need to do, but it's nice to have the option.