Welcome to LQ. ___
Please tell, which Linux, version , you are using, like
CentOS 5.4, Ubuntu 9.10, Fedora 12.
With that information included, you will get better answers.
Also please tell, which software it is, that require g++-4.0.2.
In most cases, other solutions are available.
( And a Makefile can be edited.)
On the most Linux, the Package Manager can install two to four
g++ compilers, all meant to be installed at the same time.