Vista - Help with itunes installation and MS Office on windows vista x64

Everytime I try to install iTunes I experience the following problems. I run the iTunes download for Vista x64 from the iTunes website. Then after it is downloaded and I go to run it I get the following Windows Installer message: "This installation package could not be opened. Verify that the package exists and that you can access it, or contact the application vendor to verify that this is a valid windows installer package". I have called Apple to no avail, I have contacted Dell since this is a new Dell Insipron 530s computer, they want $239. to fix. I have changed the windows installer to automacic vice manual - no luck. I just need help in installing iTunes and while I am at it, Microsoft office 2007 student teacher edition. This is really getting frustrating. Thank you.