If you configured an SNMP write community string then it is possible to change the password using a solarwinds products.
http://solarwinds.net/Tools/Professional+/Categories/Cisco_Networks.htm
I have changed password on a cisco cat 4003 successfully, here are some notes
The TFTP server has to reside on the same net as the device.
In the case of the 4003, I had to replace the unknown password with another known encrypted password. It did not take a password string or a delete.
I tried it in the lab before doing it in production.
Tony K.