Not at all, you do not have to buy windows....
And sun virtual box is very well supported. I find it to work as well as vmware workstation, I have used it on both pc and linux.
Download the microsoft windows TEST images. They are full versions of windows used for evaluating the OS. They have versions for testing versions of IE and other aspects. Regardless they expire every few months, at which point you can just download the next image. If all you are doing is simple stuff, and you don't own/want to buy a copy of windows, this can be a good option for you. Just configure your VM to have a seperate partition/drive that will persist and store all of your applications/files there if you go this route.
Good luck =)
Current image Expires January 11, 2011
http://www.microsoft.com/DOWNLOADS/e...displaylang=en