ITunes will NOT open from shortcut, cannot be updated to newer versions!

Question

So I haven't changed computers and I'm pretty sure I hadn't uploaded a new version of iTunes when this happened, but...
One day it just wouldn't open from the shortcuts (like on the desktop and the start bar). It took me forever to realize it still opens when I go directly to its source and click on it, but it still gives me this box:
{iTunes Setup Assistant}
Warning!
iTunes was not properly installed. If you want iTunes to be able to retrieve CD information from the Internet, you need to reinstall iTunes.
(OK)
So I did try reinstalling it, but nothing seems to work.
And when I do try from a shortcut, this is the series of windows I get:
{Windows Installer}
Preparing to install...
(Cancel)
{iTunes}
Please wait while Windows configures iTunes
(Cancel)
Gathering required information...
[status bar]
{iTunes}
Error writing to file: C:\Program files\iTunes\iTunes. Resources \nb.lprof\EA0423.rtf.
Verify that you have access to that directory.
(Retry)(Cancel)
If I click Retry, it just keeps opening the same window over and over. So then I click Cancel and get:
{Problem with Shortcut}
A fatal error occurred during installation.
{OK}
And if I try to install updates, I end up INSTALLING all of it but at the very end I get:
Errors occurred while installing the updates. If the problem persists, choose Tools > Download Only and try installing manually.
Please help? This is so annoying!!

Answer 1

Thank you to Polydorus! I was disheartened to see that the person posting the question wasn't getting results, but I thought I'd try the first round of easy suggestions provided by Polydorus.
1. I did a disk check (see right-click c drive, etc.). this found no problems, so no solution
2. I did the following: "The try a repair install of iTunes. (Find iTunes in Add/Remove programs and select change>>repair.)" This did it's magic! the warning which included "...If you want itunes to be able to retrieve CD information from the Internet, you need to reinstall it" no longer appears. I recommend anyone with this warning popping up each time you open itunes on a windows machine give this a try.
Thanks again!
Another Coop