I remember there was a way to do this on the 3600 using a command, but not sure if its there for 2600. Anyway your 2600 has two dram slots. I have seen both combinations. 1-32M as well as 2-16M modules.
The link below -
http://www.cisco.com/warp/public/63/simm_config_3620_3640.html
Clearly indicates it does not work on a 2600 platform. You could try "show platform" on the router and see if it yields you anything.
Also use this link to install the RAM.
http://www.optimumdata.com/shop/files/cisco/2600/2600_Series_Mem_Upgrade_Config_Note.pdf
Sankar Nair
UC Solutions Architect
Pacific Northwest | CDW
CCIE Collaboration #17135 Emeritus