since gcc is a core part of your operating system don't try to upgrade/downgrade your core gcc. When you need another version of gcc
just use the version you have to compile the new one and install in a safe place like /opt/gcc3.
use these instructions and follow them to the letter for a working version of gcc 3.3.6
to use your gcc3 like the instructions say you can use these shell variables
or adjust the PATH variable to start with /opt/gcc-3.3.6/bin
with something like