I don't quite understand what you are looking to do here, or your setup. Do you 1 drive with 285 GB and another with 1TB? In that case you can remove the small one without affecting the 1TB. If you have a 1 TB drive with a 285GB partition and a second partition for the rest of the space (sounds more likely give the odd size) you could delete the small partition and then expand the other partition but you will loose all the files in the 285GB partition unless you copy or move them somewhere else first.