Mozilla CEO Objects To Safari Auto Install
When installing Quicktime on the PC it always asks you about which files you want to associate with it. You are presented with two quick options, Quicktime media only or all media files. If you wish you can manually go through a tree of check boxes to select exactly which file types should open with it. Quicktime media only is the default. Now if you buggered around with this without actually reading the dialogue then it's your own fault that you fail. The default was sensible and you changed it.
Quicktime repeatedly checks its file associations and if it finds them different to how you originally set them it will ask you if you want to put them back. This is due to Microsoft's stealing media file associations, even those Quicktime ones it could not play away from Quicktime. This hampering of Quicktime was brought up in the anti-trust trial against MS.
If you want to run .Net applications you need the .Net framework installed. Quicktime is not just a media player but a media application framework. iTunes uses this framework for media playback, so without it iTunes can't work.
Everyone has the same problem? Me myself and I?
Seriously Apple has a lot to learn about writing software for Windows, like how to use standard system window chrome and menu bars. But your problems are down to borked file associations that you very likely caused yourself. I've installed Quicktime on every PC I've used for the past 5+ years, never had any of such problems. But perhaps that's because I'm in the minority who actually read the dialogue my computer has to tell me.
Did you know you can even open up the Quicktime Settings utility and change them all again?
While we are suggesting moderation for posts in this thread. Can I point out that being condescending is not an option, but being informative is :)