Can't update or delete iTunes

I have a Toshiba Satelite laptop running Windows 7 (64 bit). I have been trying unsuccessfully to update iTunes, iCloud Control Panel and Quicktime. I even tried to delete these programs before installing the updates, but nothing. I keep receiving the following message no matter what I do:

"Error writing to file: C:\Config.Msi\20e765.rbf Verify that you have access to that directory."

I own the laptop and have administrative priveleges in Windows. I don't understand why I am receiving this error message. Can anyone help? This is FRUSTRATING!!!

Thanks,

Paul