4. edit the Registry Key and import it
Save the file (in my example "gs.reg") with the imported registry key in a different file (in my example "gs6432.reg") and change the registry keys in the file as follows:
4.1.) HKEY_LOCAL_MACHINE/SOFTWARE/AFPL Ghostscript
to HKEY_LOCAL_MACHINE/SOFTWARE/Wow6432Node/AFPL Ghostscript
4.2.) HKEY_LOCAL_MACHINE/SOFTWARE/AFPL Ghostscript/8.53
to HKEY_LOCAL_MACHINE/SOFTWARE/Wow6432Node/AFPL Ghostscript/8.53
After the change my file gs6432.reg looked like this:
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE/SOFTWARE/Wow6432Node/AFPL Ghostscript]
[HKEY_LOCAL_MACHINE/SOFTWARE/Wow6432Node/AFPL Ghostscript/8.53]
"GS_DLL"="C://Program Files//gs//gs8.53//bin//gsdll32.dll"
"GS_LIB"="C://Program Files//gs//gs8.53//lib;C://Program Files//gs//fonts;C://Program Files//gs//gs8.53//Resource"
Import the new file into the registry database. To achieve this, launch Windows Explorer and right-click on the file. In the context menu choose "Merge".
Explanation for 4.
If you acces the registry of Windows XP x64 from a 32-bit application and this 32bit application wants to read the registry-key "HKEY_LOCAL_MACHINE/SOFTWARE", then Windows XP x64 redirects the 32bit appliation to a node (a registry-key) called "HKEY_LOCAL_MACHINE/SOFTWARE/Wow6432Node".
As FreePDFXP and the setup programm of FreePDFXP are 32-bit software, these programs can find Ghostscript x64 only with the registry entries in your gs6432.reg file.
Alternative
Alternatively you can install the 32-bit version of Ghostscript. RedMon always must be installed as a 64-bit Version.
You may download the files gs.reg and gs6432.reg here:
gs.reg gs6432.reg