1. Where do i obtain new kernels in ".rpm" format to update my RHEL5?
is it only available to RHN subscribers?

2. i downloaded latest kernel (linux-2.6.31.5.tar.bz2) from kernel.org.
#tar -xjvf linux-2.6.31.5.tar.bz2
after this i have a directory with lots of stuff in there. how do i use this directory ?

3. for example..made by openVz, centos, fedora, debian
can any of these be used to update any flavor of linux?

Sign up with Red Hat. Pay them. Do what they say to do, or simply let them do it all for you automatically. There is a reason for what they do, and they happen to do it very well.

I say in all seriousness (and with no disrespect intended): "Do not trifle in the affairs of dragons, for thou art crunchy, and taste good with ketchup."

i am learning to update kernels .
i would like to know what is the procedure to do it and what is compatible with what

thanks

1. No, you just have to use the facility for rpms should be called rpm...

rpm -options something.rpm

2. can't really... or more precisely won't really help with this one, there should be a manual somewhere with instructions on how to set it up, look for a readme document, I am not going to advise anymore then that as this sounds like an easy way to cause issues.

3. No, there are unofficial repositories that can be used for Red Hat but generally if you aren't going to pay for a RHEL license you should use CentOS as it's the nearest thing to clone around that is completely free. Repositories for pack managers generally do not work, across distribution.

1) Cant rally help with that. I don't use RHEL5

2) What you downloaded is kernel source code. You can compile it and create your own kernel. There are tons of guides on internet on how to do it.

3) Theoretically yes. But not all uses rpm packages so it might be difficult to update. But i wouldn't recommend it.