Most of Rhino's settings are not stored in external files, but in the registry. Because there is not one single file that contains all options and personalizations, you will have to do a bit of work to transfer all of your custom settings. There do exist some shortcuts:
The easiest way to transfer the bulk of your settings is to use the Rhino command ExportOptions, which creates a single file with MOST of the user customizations. Importing this file into another installation via the command ImportOptions will transfer most common settings.
Display modes are not included in the ExportOptions, you need to export them separately! You do this from Options > Appearance > Advanced Settings.
The workspace file (.tb) contains all the toolbar customizations, one can copy this between installations as well.
Other things that might have been modified could be your template files, display modes, installed plug-ins, etc.
A general transfer procedure might look like this:
ExportOptions - creates an .ini file
Make a copy of your workspace (.tb) file if you customized it
Make copies of any custom template files you created
Export any custom display modes (if you created any) - creates one .ini file per display mode
Make copies of any other external files used, including:
Non-standard plug-ins
E-maps
Scripts
etc.
ImportOptions and import the .ini file created by ExportOptions
Copy your workspace, template, emaps, scripts, plug-ins files to appropriate locations
Tools>Toolbar Layout and load your custom workspace
Go to Options > Appearance > Advanced Settings and import any custom display modes created, one by one
Drag n' drop your extra plug-ins into the Rhino window to install (some need an external installer, use that if necessary)
Set Rhino up to open with your custom template.
In the Files section of Options, set file paths to scripts, templates, etc. if they are non-standard.