PowerPoint registry settings

I have a user who uses an IBM laptop. It runs Windows XP Pro and he is an administrator of the machine.
He has a problem with trying to open some Powerpoint presentations. The error that comes up says "You are attempting to open a file that is blocked by your registry policy setting."

He can see the presentation in the preview window of the first page, but it will not let him open the file. It's a local file, so he should be able to see it since he is an administrator.

Any ideas?