iTunes Installation issue (64bit Win7)

Today I was required to update iTunes so I could activate my new iPod, keeping in mind until this point iTunes had worked fine on my system. Anyway, I downloaded the latest patch and attempted to install it. During the install process at the point saying "Status: unscheduling apple update" I get this message

"There is a problem with this windows installer package. A program required for this install to complete could not be run. Contact support personnel etc"

I downloaded the 64bit itunes version........can someone please explain what has happened and how I can get around this issue so I can just listen to my music?