I use the Linux version of Vmware on my computer but, there are alternatives. I have heard Bochs occasionally mentioned as an open source alternative. There was also a recent anouncement about CoLinux. I am not sure if CoLinux is something that is available and ready to be used or not. There is also the Vmware like product that was recently bought out by Microsoft but, I can not remember what that is called. The only one that I have ever used and know much about is Vmware. I barely even know what the other alternatives are.
Bochs is an open source PC emulator that is capable of running most Operating Systems inside the emulation. http://bochs.sourceforge.net/
Cooperative Linux is something new that that claims to be able to run Linux on Windows and somhow do it without using a commercial PC virtualization software such as VMware.
There are several versions of Vmware. One version of Vmware workstation is used to run Linux or other operating systems under Windows. The is another version that that is used to run Windows or other operating systems under Linux. One thing that I do not like about the Linux version of Vmware is that it is a pain to configure it correctly to share USB or Parallel port devices such as printers and scanners. I suspect that it might be easier to do that under the Windows version of VMware but I am not sure. Another thing that I dislike somewhat is that Vmware does not support all versions of all Linux distros. I use Vmware and would not want to give it up but, I am just warning anyone reading this that configuring every last detail perfectly might might be difficult. By the way, there are also other versions of VMware that are designed for use by large companies.