i need a help to install the gcc-4.5.1 or gcc-4.5.1.tar.bz2
I am using Red-Hat
It would be very helpful if you told us what Linux distribution you're using! You may not even need to unpack one of those annoying tarballs. Look in your distro's own repository, using the package manager. If you don't find it there, write back and tell us what distribution.
Since gcc 4.4.4 is the latest available in Fedora 13, I don't think it will be in the RedHat repos. I know that it's usually as simple as unzipping the file, then, doing make and make install, but, when you unzip the file, there should be a Readme file, that file will give you the compiling instructions.
I have also checked the fedora package search at https://admin.fedoraproject.org/pkgdb/search/ and found that no packages for GCC are available in the repo.
With that being said we can get to the build process, gcc is in fact using the (./configure, make, make install) method for building and installing the application. But this application also have many options which can be included in the ./configure command so you will need to read all documentation in the archive you downloaded to determine your specific needs. You can refer to the slackware-current gcc build script http://slackware.mirrors.tds.net/pub/slackware/slackware-current/source/d/gcc/gcc.SlackBuild for an example of working options and steps used for compilation.
I am running CentOS 5.5 (same as RHEL 5.5) and just built gcc 4.5.1. There are a bunch of pre-requisites to build/install first and the entire process (if you run all of the tests) will take about 2 days. In any case, you will have to build from source, and I STRONGLY recommend that you use the gcc 4.4.x compiler (currently 4.4.0-6 on el5) to build it, not the default 4.1.2 compiler that is the default gcc tool chain. I tried with 4.1.2 first, and had to redo it with 4.4.
FWIW, my wife is a senior physicist working in the computer division of a major physics research lab and had to build 4.5.1 this week on Scientific Linux (a version of RHEL 5). She had a HUGE number of problems getting it all sorted out on their systems, a lot of which will be used by the LHC at CERN to analyze output from the LHC. We had an interesting time sharing our pain and suffering in this process - I am a professional consulting software engineer and work almost exclusively in Linux/Unix systems for major manufacturing corporations.