Author's description, including installation instructions:
I got frustrated at Netscape's inability to delete items from its helper
applications list, and its occasional inability to associate correctly a MIME type with a file type on its popup menu. I hacked together this ResEdit TMPL to bypass the helper applications dialog entirely.
To install: use ResEdit to copy these TMPL resources into your Netscape Preferences file.
To use: To edit the helper applications list, open the MIME resources in the Netscape Preferences file with ResEdit. The SMIM resources in the Netscape Preferences file are used for the telnet, tn3270, and "View source..." applications. Note that the name of each MIME resource must match the "MIME type" field in the TMPL.