config.msi and folder permission preventing Installation

Please help - i have been using iTunes for many years and i was extremely happy with the product unitl recently. I tried to update the version of iTunes but it returned an error and asked me to download the manual version. this was completed and run (as an administrator) where i was again given an eror - you do not have permission to J:\config.msi Checking the permissions i noted that the folder only had read permisssion, this was changed and the install run again. the same error occured. I check the folder's permissions and it hadd reverted back to read only access!

I went to extremes - i uninstalled ALL apple products as per instruction on your site (discussion post - Topic: can't install 7.6 due to config.msi access error message)- restarted the machine - ensured that the file were not present, then tried again SUPRISE - it did not work - same error! this has been repeated and i am now at a complete loss.

Please help as my ipod is now an expensive paper weight!