[deftoned]

We had the same problem when developing the website for my place of employment (see here). You are never going to be able to stop people browsing with a maximized explorer window, so we gave our window a definite edge, and shadowed it over the background. I think it works quite well. It means that the centre bit can stay a fixed size, and you reduce the white space by filling it with what ever

Could look something like this, with a subtle pattern on the background to kill the white space...



Just a suggestion, I won't be offended if you hate it