* C:\Temporary Internet Files\Content.IE5 is not a default directory under Vista, so it is curious where it originated from.
* Open Internet Explorer and go Tools->Delete Browsing History. Click the Delete All button for Temporary internet Files, confirm the deletion, and then try downloading/installing a program again.
* If the problem remains, see if you can browse to that location using Windows Explorer. (Through (My) Computer.) You may need to enable the viewing of hidden files/folders, as well as system files/folders. (Viewing options can be found by going Organize->Folder and Search Options->View.)
* If you can browse to that location, try using MoveOnBoot to delete the file.
* Back in Internet Explorer, go Options->Internet Options and click Settings under "Browsing options." Let us know the "current location" it lists.
* Have you tried double-clicking the downloaded application installer instead of simply clicking Run when Internet Explorer presents you with the option?
Let us know how it goes.
John