Q: You need to get GCC 3.4.2, so you downloaded the source, and you're trying to use your existing GCC 3.4.5 compiler to build it, correct?
Q: The first step to building 3.4.2 is to run "./configure", and that's where you got the error "" command not found", correct?
1. It would be easier if you could simply find a 3.4.2 binary for your system. For example, an .rpm. Please try that, OK?
2. Otherwise, please confirm that you actually HAVE a viable compiler. Type this, and cut/paste the output:
3. Finally, look at the comments at the top of your "configure" script (or at the README that accompanies it) and see if it takes any command line arguments that might help.
4. Please post back what you find. Please cut/paste exact commands and exact messages.