I hadn't heard of ReactOS before, but it looks pretty interesting: http://www.reactos.org/xhtml/en/index.html

hal, how well does ReactOS work at this point?

As being around version 0.2.9, don't expect too much. It's not yet suitable for regular use. Some applications work quite stable, Firefox amongst those, others might even kill the whole system. I.e. if you try to edit the registry in current nightly builds it gets fried. A few drivers for video, networking and sound work, but installing them isn't as comfortable as in Windows.. Their aims for 0.3 are stable networking and Plug&Play.
Their nightly builds can be found at
http://svn.reactos.com/iso/
If you want to give it at try, put an iso on a CD, boot from it and install on a spare harddisk. Reactos can also be run in the emulators / virtual machines. On the sourceforge page there is also iso image which boots Reactos directly from CD.

Well, well, well, this is interesting. I didn't know that ReactOS was able to run DOSBox. Just goes to show how fast open source software can progress. 😀