You take much less of a performance hit when you virtualize your hardware instead of emulating hardware in software. The most popular virtualization applications that I know of are vmware, Xen and Virtual PC. VMware is a very nice commercial solution. In my opinion it is well documented, has a great community and seems to be really stable. If you plan on using virtualization for home use, I have a free way for you to do it on the next slide, but if you plan to use it for business, please send these people some money. I think they deserve it for such a nice product. Xen is an Open Source project that should do much the same as VMware. They use what they call a "paravirtualized" approach which seems to make the performance even better than VMware, with the caveat that the guest OSes have to be ported to run within Xen. Microsoft Windows guests are only supported through a side mechanism made to run unmodified guest operating systems which carries a little more performance penalty. Xen is pretty new on the scene, but I'd expect it to become more and more popular as it matures. I think Fedora Core 5 has Xen support built in. I do not recommend Virtual PC on principal alone.