Done! I updated IOS and installed some cryptographic options that will allow IPSec encryption and high-security VPN access. I plan on replacing the router with something a little beefier next month.
Quote:TWN-Router#sh ver
Cisco IOS Software, C1700 Software (C1700-ADVSECURITYK9-M), Version 12.4(25c), RELEASE SOFTWARE (fc2)
Copyright (c) 1986-2010 by Cisco Systems, Inc.
Compiled Thu 11-Feb-10 22:20 by prod_rel_team
ROM: System Bootstrap, Version 12.2(4r)XL, RELEASE SOFTWARE (fc1)
TWN-Router uptime is 0 minutes
System returned to ROM by reload
System image file is "flash:c1700-advsecurityk9-mz.124-25c.bin"
This product contains cryptographic features and is subject to United
States and local country laws governing import, export, transfer and
use. Delivery of Cisco cryptographic products does not imply
third-party authority to import, export, distribute or use encryption.
Importers, exporters, distributors and users are responsible for
compliance with U.S. and local country laws. By using this product you
agree to comply with applicable laws and regulations. If you are unable
to comply with U.S. and local laws, return this product immediately.
If you require further assistance please contact us by sending email to
export@cisco.com.
Cisco 1760 (MPC860P) processor (revision 0x500) with 53479K/12057K bytes of memory.
Processor board ID FOC064006W0 (3619802113), with hardware revision 0000
MPC860P processor: part number 5, mask 2
2 Ethernet interfaces
1 FastEthernet interface
32K bytes of NVRAM.
32768K bytes of processor board System flash (Read/Write)
Configuration register is 0x2112
Sadly, this killed off ~2 years of router uptime.

-b0b
(...IPSec for the win!)