Hi Hugo,
You can narrow this down to the two default rings (that are in the phone hardware) by probably just renaming the file so the phones can't find it. You could also use the process shown below to actually edit out all the rings that you don't want;
The Cisco Unified IP Phone ships with two default ring types that are implemented in hardware: Chirp1 and Chirp2. Cisco Unified CallManager also provides a default set of additional phone ring sounds that are implemented in software as pulse code modulation (PCM) files. The PCM files, along with an XML file (named Ringlist.xml) that describes the ring list options that are available at your site, exist in the TFTP directory on each Cisco Unified CallManager server.
The following sections describe how you can customize the phone rings that are available at your site by creating PCM files and editing the Ringlist.xml file:
The Ringlist.xml file defines an XML object that contains a list of phone ring types. This file can include up to 50 ring types. Each ring type contains a pointer to the PCM file that is used for that ring type and the text that will appear on the Ring Type menu on a Cisco Unified IP Phone for that ring. The Cisco TFTP server for each Cisco Unified CallManager contains this file.
The CiscoIPPhoneRinglist XML object uses the following simple tag set to describe the information:
The following characteristics apply to the definition names. You must include the required DisplayName and FileName for each phone ring type.
DisplayName defines the name of the custom ring for the associated PCM file that will display on the Ring Type menu of the Cisco Unified IP Phone.
FileName specifies the name of the PCM file for the custom ring to associate with DisplayName.
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Note The DisplayName and FileName fields must not exceed 25 characters.
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This example shows a Ringlist.xml file that defines two phone ring types:
Analog Synth 1
Analog1.raw
Analog Synth 2
Analog2.raw
From this doc;
http://www.cisco.com/en/US/products/hw/phones/ps379/products_administration_guide_chapter09186a0080799741.html#wp1088056
Here is some additional great info from Sankar;
http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Unified%20Communications%20and%20Video&topic=IP%20Telephony&CommCmd=MB%3Fcmd%3Dpass_through%26location%3Doutline%40%5E1%40%40.1dde5ab6/2#selected_message
Hope this helps!
Rob
