Depending on what 12.4.15 release you are, this may be a license issue.. Please refer to this thread..
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"The essence of christianity is not the enthronement but the obliteration of self --William Barclay"
Had a similar issue in my lab , I did want the license. Instead i downgraded the IOS and without the demo license.
The below IOS does not require gatekeeper license:
Cisco IOS Software, 2800 Software (C2800NM-IPVOICE_IVS-M), Version 12.4(4)T7, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2006 by Cisco Systems, Inc.
Compiled Tue 28-Nov-06 18:37 by kellythw
ROM: System Bootstrap, Version 12.4(13r)T, RELEASE SOFTWARE (fc1)
HQ uptime is 2 weeks, 4 days, 12 hours, 27 minutes
System returned to ROM by reload at 07:28:44 PST Fri Jan 24 2014
System restarted at 07:29:49 PST Fri Jan 24 2014
System image file is "flash:c2800nm-ipvoice_ivs-mz.124-4.T7.bin"
Kidnly rate the post accordinly.