Well, the approved, sanctioned, and safe way would be to do a library restore. This is found at File->Library->Restore Library.
MC does library backups automatically from time to time. You can also do one manually through that menu before you uninstall. Restore library also allows you to move MC to a new PC, if your paths are compatible. It will restore all your MC settings, including equalizers, and the references to the library contents (but not the media files themselves).
The more surgical, unsafe, use at your own risk method... to be used only if you know what you're doing and will take responsibility for your own actions...
Export/Import from the registry the following: HKEY_CURRENT_USER\Software\JRiver\Media Center xx\Zones\Global\Equalizer\Presets where xx is your version of Media Center. You'll see the key there on a system with MC installed. This will target ONLY your equalizer preset definitions.
Be aware there are also settings in the Equalizer key for each zone:
HKEY_CURRENT_USER\Software\JRiver\Media Center xx\Zones
that indicate which equalizer preset is actually selected. However, these will be overwritten when you select a preset. All your other DSP settings for the zone are also stored in this key.
So close MC, import the Global\Equalizer\Presets key, start MC, then select the preset you want to be active, and it will update. When I say close MC, I mean completely close it: Media Server should not be running, so check your system tray.
If you bork your MC installation doing this, don't come back complaining. That's what the nice friendly "Restore Library" function is for.