This is a common issue with Vista (and maybe Window 7). If you search the forums for 'create eqhost', you will get quite a few threads, e.g.
http://www.eqemulator.org/forums/sho...=create+eqhost
Basically run notepad as administrator, or don't install EQ into Program Files, but something like c:\everquest should get around it.
The guide should really be updated to mention this as it comes up so often.