Its long been known that you can use something like the User Agent Switcher to make it appear like you're using a different operating system than you really are. This can be useful on some websites that insist you need to run Windows - when in fact Linux or practically any other operating system will work fine.
But for those sites that are actually telling the truth, you can often run Firefox under WINE with very good results. Just head over to www.getfirefox.com and download the Windows binary. The site actually does its own OS detection, so you'll probably want to choose "Other Systems and Languages." Once you have it, make sure you have WINE installed. I also installed the MS truetype fonts because it looks terrible otherwise.
# apt-get install wine msttcorefonts
And then start the installer
$ wine Firefox\ Setup\ 22.214.171.124.exe
You'll go through the normal install process, and when you're finished you'll see a new Firefox icon on your Linux desktop:
Double-click it and you should be good to go! If you want to visit a site with audio, you'll want to run winecfg, visit the Audio tab, choose your settings (I just left the defaults) and click Apply. Otherwise you might run into some issues with Firefox crashing. If its any consolation, Firefox will crash on certain sites powered by Move Networks in Windows, too, if there is no audio driver installed. This is probably related to the Firefox extension you must install to view the site.