Typically NZB's put into Newsbin get stored temporarily in the NZB's folder in the data folder. You can get at the data folder from the main options.
I’ve tried different folders and different drives.
This doesn't have anything to do with specific drives but it might depend on whether you're downloading and unraring into the SAME folder or downloading and unraring into DIFFERENT folder.
For example, if you have the download path set to
"Z:\Download\"
and have no unrar path set, it'll download and unrar into that path.
On the other hand if you have the download path set to:
"Z:\Download\"
and the unrar path set to
"Z:\UnRAR\".
It'll unrar from "Download" to "UnRAR". This gives you the cleanest unrar. When you download and unrar to the same folder. Newsbin uses a temporary folder to unrar into and copies the files out to the main download folder after the unrar. Because sometimes the contents of the RAR file have the same names as the RAR's themselves.