QEMU: a Multihost, Multitarget Emulator
QEMU may lack the graphical configuration and VM setup tools of commercial programs like VMware, but I have found it to be an excellent solution to the I-need-to-run-just-one-Windows-application problem. Judging from the comments I've read on the QEMU forum and on the #qemu channel on the Freenode IRC network, QEMU is well suited to solving many other problems. Give it a try, I think you'll like it.
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Daniel Bartholomew has been using computers since the early 1980s when his parents brought home an Apple IIe (with an 80-column card!). After stints on Mac and Windows machines, he discovered Linux (Slackware) in 1996 and has been using various distributions ever since. He lives with his wife and children in North Carolina.