Create a console connection.

Turn On Router. Send "Break" Message (In CRT is at Edit/Send Break)
When this is done, this should appear:

System Bootstrap, Version 12.4(13r)T, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 2006 by cisco Systems, Inc.
PLD version 0x10
GIO ASIC version 0x127
c2801 platform with 262144 Kbytes of main memory
Main memory is configured to 64 bit mode with parity disabled


Readonly ROMMON initialized
rommon 1 > 

At this point type:

rommon 1 > confreg 0x2142

You must reset or power cycle for new config to take effect, so type: 

rommon 2 > reset

After loading, you can erase de startup configuration, doing the following:

enable
#copy running-config startup-config

Finally do:

S# conf 0x102 or conf 0x2102 so the register starts where it should.