When I try to compile one of the samples, it tell me I need to fill out the location of the PB compiler, resource compiler, etc. I've done all that, and checked the "default compiler" option. I also tried re-specifying the locations, but no luck.
FireFly allows you to specify different compilers for different projects.
The sample programs are probably set up to use PowerBASIC 7. You need to go in to the "Project Properties" dialog that is found under the "Project" menu and select PowerBASIC 8. There is a combobox there where you can select the compiler.