Sun's virtualbox windows binaries are under 'non-commercial' license so can't be used in any company. But source code is GPL. Is it any resource on the network that has a virtualbox compiled binaries for windows?
Added a bounty to see if I can get a little more feedback.
I don't Know what exactly you are going to do with VirtualBox but you should check if you can' t use the Personal Use Licence.
From http://www.virtualbox.org/wiki/Licensing_FAQ
It doesn't matter whether you just use it for fun or run your multi-million euro business with it. So as long as you follow some rules on distributing the Installation in your Company you will be able to use the commercial licence
Q: What exactly do you mean by personal use and academic use in the Personal Use and Evaluation License?
A: Personal use is when you install the product on one or more PCs yourself and you make use of it (or even your friend, sister and grandmother). It doesn't matter whether you just use it for fun or run your multi-million euro business with it. Also, if you install it on your work PC at some large company, this is still personal use. However, if you are an administrator and want to deploy it to the 500 desktops in your company, this would no longer qualify as personal use. Well, you could ask each of your 500 employees to install VirtualBox but don't you think we deserve some money in this case? We'd even assist you with any issue you might have.