Get a File Manager (like Astro), mount the drives to your windows machine, or use the 'My Files' application to do the following:
Remember you have your internal SD card (the 16GB one that comes with the phone, it is located in the file system on the phone as \sdcard), and your external (removable) SD card that you provided (it is located in the file system on the phone as \sdcard\sd)
you need to create a folder on the internal SD card for your ringtones.
Create the following directory:
more than likely there will be a notifications folder in the same place, just create the new folder there. Move
all your ringtones into that folder. Once the file(s) are moved, media scanner should run.
From there the ringtones will no longer show in the default media player (mine were also removed from cubed which is the player i use), but are still accessible when selecting 'Phone Ringtone' when assigning ringtones.