One difficulty with BT or emule is that, when the hard drive is full, we constantly need to move older files to a new hard drive so that we can download newer files.

We can change BT or emule's setting so that the folder for downloading points to the new hard drive, but then, what if emule haven't finished downloading for some files that are hard to find, and it is 92% done... in that case, we would like to keep the old setting so that when the last 8% arrives, it can go into the correct file. (and same for BT, if we haven't finished some file or if we want to seed something later).

So is there a good way to let BT or emule point to 2 hard drives, or somehow let the new hard drive "merge" into the existing hard drive / folder?