HI,

My Machine is running on RHEL3, Its not booting. When I try to boot in rescue mode.Its giving the following err:

" Kernel panic : Fatal exception "

Can any one tel me how to get rid of this error?

Assuming that your OS is toasted, you could try booting from a Rescue CD such as Main Page - SystemRescueCd and that will give you access to your system at least.

Since you're running RHEL3, you may try contacting RedHat for support. According to their website they offer maintenance support for RHEL3 through 2010. See below (source: redhat.com | RHEL Errata Support Policy)

Red Hat Enterprise Linux (version 3):

Including Red Hat Enterprise Linux AS, Red Hat Enterprise Linux ES, Red Hat Enterprise Linux WS, and Red Hat Desktop

General Availability: Oct 23, 2003
Full Support (including hardware updates): Oct 23, 2003 -- April 30, 2006
Deployment Support: May 1, 2006 -- Jun 30, 2007
Maintenance Support: Jul 1, 2007 -- Oct 31, 2010

through rescue mode also it gave the same error.

Do you mean you booted from the Rescue CD I suggested and you got the exact same "Kernel panic : Fatal exception" error? If you did, then sounds like your machine is failing POST and its a hardware problem. One simple thing you can try is to reseat your RAM...just take it out and put it back in again making sure it's in securely and reboot. Also, if you have known good RAM around that you can put in, I'd try that too. It's possible your CPU is toast. If you have another identical or similar box you can put your hard drive in, try that too.