The OpenEdge Hive

There are P4GL functions for setting and getting registry information. I am not familiar with those P4GL functions so it may be silly to use Windows functions instead.

One thing the P4GL can not do is accessing (hexa)decimal data.
Before you try to access the registry directly you should try to find some specialized API call for the requested information type.

For example:

You can read a list of available printers from the registry, but you can also use the EnumPrinters API function for this task. It is generally speaking better to use the API function, because these are documented while the exact registry-locations are not. The EnumPrinters example is only one example. I don't know, but I guess there are documented functions for everything in the registry.
The point is, I think you should try to find an API function before you start digging in the registry directly. Unless of course you are writing and reading in your own key.