I've added a few descriptions of the various forums to the main forum page. There were many situations where it was unclear which forum was best suited for a specific topic. Hopefully those descriptions will help make choosing the proper forum less ambiguous. The better organized the forums are, the more likely someone is to get a helpful answer, and the more likely it is that someone will find a previous answer to their problem.
I based those descriptions upon how the majority of people have been using the forums. For example, most (but not all) discussions about PPS, 321, SoB/PSP and CW sieving have been done in the individual subproject forums rather than the "Sieving" forum, so the description for the Sieving forum says that it's for PSA manual sieving and not BOINC sieving.
To provide guidance for some of the more ambiguous situations, here's where things belong best:
1) If the topic is specific to a particular subproject, it goes in that subproject's forum.
2) If it's about Manual Sieving in the PSA, it goes in the Sieving forum.
3) If it's about PRPNet or PRPNet subprojects, it goes in the Project Staging Area forum.
4) If it affects more than one subproject but has anything to do with hardware, software, etc., it goes in "Number Crunching", unless it's better suited to one of the forums in 1, 2, or 3 above.
5) Anything else related to PrimeGrid (such as discussions about the forums) belongs here in General Discussion. Topics not directly related to PrimeGrid also belong here.
6) Generally speaking, I don't really think Problems and Help is that useful as a distinct forum -- except that someone new to PrimeGrid won't have a clue where they should ask for help. This forum is for them. :)
I didn't mention the news category because only a few people can start new topics there. BOINC challenges will normally be discussed in the News forum.
My lucky number is 75898524288+1
(I am NOT an administrator anymore, so please don't PM me with questions. I can't help.)