I build rpm files from xine-lib and xine-ui sources. My processor is AMD Athelon 1800XP, but I got only i386 rpms, Do I need to change any configuration in my gcc, or anywhere else?. ( Please tell me in detail ).

My OS is Fedora Core 1.

You can use the "--target PLATFORM" option of rpmbuild to tell it to build rpms for a different CPU architecture other than the default of "i386" under FC1. If you want to rebuild a xine source rpm then you could try something like:

$ rpmbuild --rebuild --target athlon xine*.src.rpm

If you have a tarball then you could try something like:

$ rpmbuild -ta --target athlon xine*.tar.gz

rpmbuild -ta --target athlon xine*.tar.gz is works, and it gives athlon.rpm files. But installed files not works ie xine is not starting.
I think my gcc is not support athlon, I tried rum configure file in the xine-lib by the following way ( as per xine's installing instruction but that is failed.

./configure --host=k7-pc-linux-gnu
configure: WARNING: If you wanted to set the --build type, don't use --host.
If a cross compiler is detected then cross compile mode will be used.
checking build system type... i686-pc-linux-gnu
checking host system type... Invalid configuration `k7-pc-linux-gnu': machine `k7-pc' not recognized
configure: error: /bin/sh ./config.sub k7-pc-linux-gnu failed

So how can I install gcc supporting athlon ?.

Gcc recognises an athlon as "athlon" and not "k7". The problem isn't gcc not supporting building for an athlon and is more likely to be some sort of dependency. Did you take a look at the output of the configure stage when you tried to use rpmbuild? Building it manually might help find the problem. Try:

$ script configure.log
$ ./configure --build=athlon-redhat-linux
$ exit

That will save the output "./configure" in configure.log so you can look at it afterwards to see if there were any missing libraries or other errors.

An alternative would be grabbing the xine rpms from freshrpms.net and rebuilding those. You'll find them at:
http://yarrow.freshrpms.net/rpm/xine
http://yarrow.freshrpms.net/rpm/xine-lib