1) As far as the ROMplers, the answer depends on whether they do disc streaming or not. Garritan and EWQLSO use streaming, so the samples should be on the 2nd drive. The application should go on the 1st drive. ROMplers that don\'t use disc streaming like Virtual Guitarist, Groove Agent, and (I believe) Trilogy can have everything on the first drive.
2) All applications, including audio, should be on the first drive.
3) I believe best performance is acheived by having samples and the audio files you are recording them to on separate drives so the same drive is not reading and writing to itself. My understanding is that it is more efficient to have one drive reading the data (Samples) and writing to another drive (the audio files). If anybody who is more knowledgable about computer hardware disagrees with this, please correct me. I, in fact have three audio drives in addition to my system drive- one for samples, one for the multitracks that the samples get recorded to, and one for the final mixes that the multitracks get mixed down to. This may be overkill.