I think you need to start at square one and do some reading and research:
VMware Communities: A Beginner's Guide to VMware Fusion
You have nothing and without a license key, a windows install is not going to happen (legally), you could find a Linux virtual machine with simple googling and then just install it in a VM, I use VM Ware player and run XP / 2000 / and Ubuntu as virtual machines, but i do have access to the .vmx files.
MS does have evaluation copies of their software available to download in ISO format that you could install in your VM for a period of 180 days. Here's a link to download an ISO of Windows Server 2008 R2. I have never setup a VM of Win Server 2008 in VPC so I don't know if it will actually work as it's not a supported guest (or host).
You may want to switch to VirtualBox which supports Win Server 2008 as both a host and a guest. See the documentation for VirtualBox: https://www.virtualbox.org/manual/UserManual.html
In addition, Windows Server 2008 comes with Hyper V which is another virtualisation tool you may have at your disposal.
Unfortunately, without a copy of Windows to install, there is nothing that you can really do. Running a virtual machine isn't a way to get a free copy of Windows.
As others have said, you could download an evaluation copy of Windows to work with. They are good for 90 days, so plenty of time to test and see how this works. You can always reload at the end of the 90 days and get 90 more days.
Here is the link for an eval download of Windows 7 Enterprise
Windows 7 Enterprise | Trial, Evaluation, Test, Download
I just want to say thanks for all the help guys and also I have to say that I'm not trying to get things for free, I'm just interested in virtual machines and didn't know how it all worked. :)
I have another computer at home which I need to buy W7 for. Can I use the same W7 I buy for the machine for my virtual computer or do I have to buy another one?
You will need a separate licence.
Don't forget, you are not buying software, just a licence to use it, and that licence (EULA) states you can only use the software on one computer. Your virtual machine is classed as a separate machine to any other computers you have.
The only free software you'll get is Windows XP mode, which Microsoft provide for those that have Windows 7 Professional and above.
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