I have tried to keep the requirements down to a minimum - avoiding newer version of PHP and optional libraries. When unavoidable, I package the external libraries with CpmFetch, saving you trouble.
Coppermine Photo Gallery (1.3.2+) - it may work on older, but I just have not tested it.
PHP Version 1.4.1+
Apache or IIS web server (should work on others but YMMV)
Access to the CPG database
Apparently every webserver is slightly different, and some problems may be encountered if you are using IIS or even some Apache installations. These problems are noticable immediately and can be solved. See the FAQ Section and the Support section for help if this is the case.