Mazhar123,
When you reboot do you get anything before the CCCCCCCCCCC.... or is it always CCCCCCCCCC ???
Normally I have had issues when someone has set the config regerstry wrong and it is communicating at a different baud rate but it normally looks like the router is cussing at you with all sorts of strange output!
You can try resetting the different baud rates and see if you get anything else other than cccccccc that is readable.
Or, if you have another 2500 that works you could try swapping the RAM and FLASH memory and see if something is wrong with that.
Hope this might help!
E.A. Broda
CCNA, CCDA, CCAI, Network +