lab_monkey>en
lab_monkey#conf t
Enter configuration commands, one per line. End with CNTL/Z.
lab_monkey(config)#conf
lab_monkey(config)#config-register 0x2101
lab_monkey(config)#end
lab_monkey#sh ve

Ascertain that it says this at the bottom of the "sh ve":

Configuration register is 0x2102 (will be 0x2101 at next reload)

Reload the router and it will ask you if you want to save the configuration settings, state YES, and it should boot in ROM memory (boot mode).

lab_monkey(boot)#sh flash

You should see something like this but in your case it will be 2 or more partitions with the IOS on one and possibly something else on the other partition(s).

System flash directory:
File Length Name/status
1 14598352 /c2500-ik8os-l.122-19a.bin
[14598416 bytes used, 2178800 available, 16777216 total]
16384K bytes of processor board System flash (Read/Write)

lab_monkey(boot)#

Now, type this out:

lab_monkey(boot)#erase flash

It will ask you which partition to erase. Erase the one WITHOUT the IOS on it, usually its number 2. Repeat that for all the partitions except the one with the IOS on it.

Then type:

lab_monkey(boot)#config t
lab_monkey(boot)(config)#no partition flash
lab_monkey(boot)(config)#exit

Afterwhich:

lab_monkey(boot)#show version
[verify flash partition has been eliminated]

Once the flash paritition has been eliminated, change the config. register to 0x2102:

lab_monkey(boot)#conf t
Enter configuration commands, one per line. End with CNTL/Z.
lab_monkey(boot)(config)#config
lab_monkey(boot)(config)#config-register 0x2102
lab_monkey(boot)(config)#end
lab_monkey(boot)#sh ve

And again checking the last line to see if it states the config register will be 0x2102 at next reload by the sh ve command. Reboot and it should come online with no partitions:

lab_monkey(boot)#reload

It will ask you if you want to save the settings, state YES again.

Some Discussion
»correct syntax on backing up a flash file