as a moderator, i will set the record straight on my policy (or rather, interpretation of the board's rules) for my section of the board; PSX emulation.
it's ok to revive a thread if you have something useful to say. "oh i had this problem and i used the help in this thread to get it working" is not something useful. giving the answer to a problem posted 2 years ago is also not something useful. but posting something worthwhile or relevant is fine. for example, let's say someone says "my game crashes when i do X at X." it's fine to revive that thread and say, yeah i read it, but i cant get it to work; here's my situation.
it's best to make a NEW thread when your problem is different in any way (i.e. someone had an FMV crash at disc 2....but you're having it on disc 3. in that case make a new thread). it's also best to make a new thread when you are having an unrelated problem (when someone had FF7 problems dont post your own in their thread. make a new one.)
if you're having A LOT of problems with your emulation experience (i.e. FF7, Driver, and Parasite Eve all dont work) you should probably stick that in one thread. in this case it's not an individual game problem, it's more like your entire setup needs to be reconfigured. so dont post "FF7 problem!" "Driver problem!" "Parasite Eve problem!". just make one thread.
so, there you go. i think i covered it....
some people get a little TOO hyperactive on "omg dont revive dead threads!!" i've seen people freak out over a month old thread when the newly posted information was quite relevant.
in any case, use your best judgement. honestly, if you dont know, just make a new post. and if you dont know after that....add more information to your original post