Failed to Update the system Registry

I have pcs with both IE and Netscape on them. I want to be able to open up one particular HTM file with Netscape only. If if change the file types for HTM from IE to netscape I don’t get the problem, however I don’t want HTM files to open with netscape only this one particular HTM file.

If I had users to the power users group I don’t recieve the error.