Hi watchoutman,

Run the following from the command line, it will install the module you are looking for:
ppm install http://www.bribes.org/perl/ppm/GDGraph.ppd
You may also want to check out the module PPM::Repositories which you can use to add all know repositories to your PPM configuration. It may be wise to add these repositories efore installing modules so that PPM will have a better chance of finding any dependencies.

For further info have a look at A guide to installing modules for Win32.

Hope this helps.

Martin