I too have this same problem. I've been having it since some time in June.
Whenever I open iTunes I get the error:
iTunes was not installed correctly. Please reinstall iTunes.
Error 7 (Windows error 14001)
>OK
Sometimes I get two of them.
I have uninstalled and reinstalled iTunes in every way, getting rid of everything apple related in the registry and all.
I have used CCleaner, which by the way detected a TON of errors in the registry related to the Visual C++ stuff.
I continuously have a system update for some Security Update for Visual C++.
Details are:
Security Update for Microsoft Visual C++ 2005 Service Pack 1 Redistributable Package (KB2538242)
Download size: 2.6 MB
You may need to restart your computer for this update to take effect.
Update type: Important
A security issue has been identified leading to MFC application vulnerability in DLL planting due to MFC not specifying the full path to system/localization DLLs. You can protect your computer by installing this update from Microsoft. After you install this item, you may have to restart your computer.
More information:
http://go.microsoft.com/fwlink/?LinkId=216804
Help and Support:
http://support.microsoft.com
No matter how many times I instal it, it is always there.
Seeing as Apple so far has no solution for this, and the given evidence from the Visual C++ update, this is probably a Microsoft problem. Which is just great because they don't have much reason to fix a problem with iTunes.
My biggest problem is just that I just cannot sync my iPod anymore though. Which is annoying because for some while it has been not working very well and I wanted to restore it to a blank copy.