The whole time I was wondering, why do I have to install the entire Microsoft Windows in order to get IE6 or IE7 to run on my Mac. All I really need this for is to check for browser compatibility.
Sure solutions like Parallels or VMware fusion are options but if I really think about it: Windows does not allow to have IE6 and 7 run parallel, which means, I would have to install 2 virtual machines, with 2 copies of Microsoft Window, which amounts to 2 Virtual Disk Images of 2GB size each (minimum). In my Book this is overkill, just to have 2 programs.
BUT I found a very easy solution:
WineBottler this little program has everything I need. It installs even IE6 and IE7 for me, wraps it into nice little Mac app files, and I can run them just like I run any other Mac program. Parallel without having to switch back and forth of VMware and Development Environment.
IE6 works like a charm, IE7 is a tad buggy, but it does what it needs to do.
I thought I share this with all of you guys.

After so many birthing problems I decided that I post an update.
Once you click on the link, please make sure that you click on Winebottler (bottom of the screen) and not on the Darwine link.
Then, after all is installed and you start up winebottler, you might get an error message that IE6 can not be installed. Open up wine and try to install from there.
In case you just see the wineglass at the top of your screen, click on it and open up Winetricks.
There you should be able to ‘install’ IE6.
Once the install is completed or failed, open up winebottler, select IE6 again and everything should work fine.
If necessary repeat the steps for IE7.

I hope that this helps a bit better with the installation.