I want AutoCAD to start off with a set Hatch Pattern and Scale, as the default is ANGLE and scale of 1, which when you hatch something big, it takes an age to raytrace etc..
First off, it is recommended that you do not edit the "acad200xdoc.lsp" file. This file is "owned" by AutoCAD, and service packs, updates, reinstallation, etc. may overwrite this file and you will lose your changes. AutoCAD provides a mechanism for a "user" owned file that you have control of, it's called "Acaddoc.lsp". If it does not exist, create it.
Secondly, your code is attempting to set HPSCALE to a string, when it expects a REAL. The first line works OK.