Looks like the responses from many IE users in this thread have pretty much confirmed the OP's hypothesis.
But I suppose a flamey reaction should be expected to a perceived insult.
ElNeroDiablo said:
Internet Explorer isn't "installed" on every windows machine as much as it FORMS THE BASIS OF THE WHOLE FRACKING GUI WITH A DIFFERENT SKIN ON TOP!
Hell, when Microsoft got taken to court by the US Government shortly after the release of Windows 95 (yes, that friggen far back!) for default "installing" Internet Explorer in an attempt to push Netscape out of the market, Microsoft told them plain and simple that they could NOT remove the Internet Explorer code from the GUI and would have to rebuild Windows 95 from the ground up if they did when told they would have to remove it, as they used the IE kernel to drive the GUI and simply gave it a different coat of paint and name.
How very convenient for them.
It's not quite as fundamental a part of the OS as you suggest, but it is technically correct that some parts of the Windows "shell" (not kernel) depended on some modules which were claimed to be inexorably part of IE. There is no reason why this should be the case in a properly designed OS.
This once again came up when Microsoft got taken to court by the EU Government about Windows 7 coming with IE8 already woven in and Microsoft came up with the idea of the European-Only editions of Win7 having the Web Browser Installation Screen that would get (via File Transfer Protocol or FTP) an alternate browser (say, Firefox 4) and install it after the bulk of Win7 was already installed, JUST to please the EU courts so they could sell more copies of windows there.
So when you use a Windows machine (unless you're manually-building a system with a European-Only version of Win7), you get pretty much no say at all in the matter if IE is actually installed or not other than hiding the IE6/7/8/9 GUI as a choice of web browser.
Ever since it was released, Windows 7 has allowed you to easily and safely remove IE at any time without adversely impacting OS functionality, regardless of your jurisdiction.
The Browser Choice update to satisfy the EU antitrust regulators (not courts) simply made the user aware of the availability of other browsers, and offered links to their websites. No mention of FTP (as if a browser is the only kind of HTTP client that exists, sheesh).
You make out like Microsoft is the victim and the EU the bully, and that it was oh so difficult for Microsoft to decouple IE from Windows and they were really making a big concession to the EU by doing that, but the EU are a democratic institution voted for by me and my fellow Europeans; they are looking out for our rights (in between meals of lobster and caviar paid for by Steve Jobs, of course, they are politicians after all) and it was a trivial matter to add the browser choice window, Microsoft really did the bare minimum they could get away with.