Ahh, the problem is starting to come back to me.
Try extracting it elsewhere first, like your desktop and then move it.
Or try running both your extraction program and OOTP in admin mode.
I remember I had to do something specificly different with OOTP6 and vista, but I can't recall exactly what it was.
Something tells me another option is installing OOTP6 somewhere other than your program files folder.
Ahh, here we go. I found
the old online league thread on the topic. You have a number of options.