Removing and reinstalling iTunes, QuickTime, and other software components for Windows Vista or Windows 7
http://support.apple.com/kb/HT1923
Have you tried the Itunes forum to see if there are any similar stories there?
iTunes for Windows
http://discussions.apple.com/category.jspa?categoryID=150
How to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows 7
http://support.microsoft.com/default.aspx/kb/929135
950093 How to use the System Configuration utility to troubleshoot configuration errors in Windows Vista
http://support.microsoft.com/default.aspx?scid=kb;EN-US;950093
Use the Vista instructions in this to reset to default the security settings.
How do I restore security settings to the default settings?
http://support.microsoft.com/kb/313222/#appliesto
Solving setup errors by using the SubInACL tool to repair file and registry permissions
http://blogs.msdn.com/astebner/archive/2006/09/04/solving-setup-errors-by-using-the-subinacl-tool-to-repair-file-and-registry-permissions.aspx
Try right-clicking on the actual Setup.exe and selecting the "Run As Administrator" option? Do so even if your user is an Admin.
This example might or might not work for you with your program it uses the built-in Administrator account to perform the install?
"It seems that the "Run as administrator" command only gives you some administrative privileges, and they're not enough to install Java (and OpenOffice, by association). In order to get around this, you need to actually log into the built-in administrator.
Open a command prompt with admin rights by clicking start, typing cmd into the search/run box, and hitting CTRL-SHIFT-ENTER. At the prompt, type:
net user administrator /active:yes
Then log out of your regular account and back in as the built-in administrator, where you might be able to install the program. When you're done, log back into your regular account and, for security purposes, disable the built-in administrator account using:
net user administrator /active:no "
If any corruption on your machine is the cause then you may need to consider a complete reinstall of Windows itself.